The moon hangs full over the Bay of Biscay on July 5th, 1942. Squadron Leader Jefferson Herbert Greswell peers through the windscreen of his Vickers Wellington bomber, straining to see anything in the darkness below. Somewhere beneath him, German U-boats cross these waters, surfacing under cover of night to recharge batteries and race toward Allied convoys. But Greswell might as well be blind. His aircraft carries ASV Mark II radar, capable of detecting a surfaced submarine from ten miles away, but those final thirty seconds are critical.

By the time his Wellington reaches visual range, the U-boat crew hears the engines, sounds the alarm, and vanishes beneath the waves in under a minute. Month after month, RAF Coastal Command aircraft detect submarines on radar, rush to the contact, and arrive to find nothing but empty water. The statistics are devastating. In 1941, RAF Coastal Command sinks exactly one U-boat in the Bay of Biscay. Meanwhile, German submarines slaughter merchant ships at a rate of 400,000 tons per month, and Britain is twelve weeks from starvation.

The U-boats are winning. Back at RAF Chivenor in Devon, an obscure squadron leader with no engineering degree sits in a workshop surrounded by car headlights and aircraft landing lights, sketching modifications to a retractable dustbin. His commanding officers think he’s wasting his time. His fellow pilots believe he’s lost his mind. The Air Ministry engineers, who actually know physics, have already dismissed his idea as technically impossible.

What Wing Commander Humphrey Deverd Lee doesn’t know—what nobody in Coastal Command knows—is that his illegal experiment is about to change everything. Within five months, his invention will sink more submarines in the Bay of Biscay than the entire Royal Air Force managed in the previous two years. Within two years, U-boat commanders will refuse to surface at night, even when their batteries are dead and their crews are suffocating. German sailors will call the Bay of Biscay “the Valley of Death.” Admiral Karl Dönitz will lose so many submarines that he temporarily withdraws his entire U-boat fleet from the North Atlantic.

And it all starts with a middle-aged officer, a car headlight, and an idea every expert in Britain says cannot work. To understand why Britain is losing the Battle of the Atlantic in 1942, you need to understand the U-boat’s greatest advantage: darkness. German Type VIIC submarines cannot win a fair fight. On the surface, they’re slow, fragile, and carry only fourteen torpedoes. Submerged, they’re nearly blind, crawling at seven knots with batteries that die after ninety minutes.

But at night, they’re lethal. The U-boat commander surfaces under darkness, recharges his batteries, races ahead of the convoy at seventeen knots, and submerges before dawn to attack from perfect position. For the first two years of war, RAF Coastal Command cannot touch them. In 1940, Air Vice Marshal Frederick Bowhill becomes commander-in-chief of Coastal Command and faces an impossible problem. His aircraft can find submarines with radar, but radar only gives you bearing and distance.

At night, when the pilot finally sees the submarine, it’s already diving. The attack window lasts exactly twenty-three seconds—the time between visual acquisition and complete submergence. No crew can close that gap. The British try everything: dropping flares, installing powerful engines, developing acoustic torpedoes, training crews to attack faster. Physics doesn’t care about training.

Month after month, Coastal Command crews make perfect radar approaches, arrive precisely on target, and attack empty water. Squadron commanders file reports listing “probable damage” or “oil slick observed.” The Admiralty knows the truth: they’re hitting nothing. By spring 1942, the experts agree there is no solution. The head of the Coastal Command Development Unit, the RAF’s elite innovation squadron, concludes that successful night attacks on surfaced submarines are technically unfeasible.

Then Humphrey Deverd Lee arrives at the development unit and starts asking uncomfortable questions. Lee is forty-four years old—ancient by RAF standards. He learned to fly in the Royal Flying Corps during World War I, then spent twenty years bouncing between squadrons, never quite fitting in, never quite getting promoted. He lacks formal engineering training and has no degree in physics or mathematics. What he has is 1,500 hours flying maritime patrols and a stubborn refusal to accept expert consensus.

In January 1941, while stationed at the Coastal Command Development Unit, Lee attends a technical briefing about the night attack problem. The engineering officer explains with charts and equations why it’s physically impossible to illuminate a submarine target at night without warning it first. Flares descend too slowly. Landing lights draw too much power. Flash bombs would blind the pilot.

Lee raises his hand. “What if we mounted a powerful searchlight on the aircraft and turned it on at the last second?” The room goes silent, then everyone laughs. The engineering officer patiently explains that aircraft generators cannot power a searchlight strong enough to illuminate a submarine from attack altitude. Even if they could, the weight would make the aircraft unflyable. Even if it didn’t, the battery pack required would take up the entire bomb bay.

The idea violates three separate laws of electrical engineering. Lee nods politely. Then he goes to his workshop and starts building it anyway. He has no authorization, no budget, no team—just a growing certainty that the experts are wrong. Over the next four months, while officially performing his regular duties, Lee converts car headlamps, salvages aircraft landing lights, and tests increasingly powerful carbon arc searchlights mounted on retractable housings.

His fellow officers think he’s having a breakdown. His commanding officer threatens him with disciplinary action for wasting military resources. On June 3rd, 1942, Lee flies his first operational mission with his jury-rigged searchlight installed in a Wellington bomber’s bomb bay. That night, he changes naval warfare forever. Squadron Leader Humphrey Deverd Lee should not exist.

Born in Aldershot in 1897, the son of a vicar, Lee joins the Royal Flying Corps in 1916 and flies reconnaissance missions over the Western Front. When World War I ends, he resigns his commission and disappears into civilian life. Most of his fellow pilots assume he’s done with flying. Then September 1939 arrives. Britain declares war on Germany, and forty-two-year-old Humphrey Lee walks back into an RAF recruitment office and asks for his old job back.

The RAF is desperate for experienced pilots, so they overlook his age and lack of combat decorations. They post him to Coastal Command, the maritime patrol force everyone considers a backwater assignment. Fighter Command pilots become celebrities and Bomber Command crews earn glory over Germany, but Coastal Command crews fly endless patrols over empty ocean, searching for submarines they can rarely find and almost never sink.

Lee doesn’t care about glory. He cares about math. During his first year back in service, he flies more than 300 hours of anti-submarine patrols. He fills notebooks with calculations—radar detection ranges, aircraft approach speeds, submarine dive times, visual acquisition distances. His fellow pilots think he’s obsessive. His squadron commander thinks he’s wasting time that should be spent drinking in the officer’s mess.

But Lee sees something nobody else sees. The math works. The timing works. The only missing piece is light. The breakthrough comes on a routine night patrol in December 1941. Lee is flying a Wellington when his radar operator picks up a submarine contact.

Lee begins his approach: slow descent, engines throttled back, perfect course. Half a mile from the target, his co-pilot spots a fishing boat with its lights on. For exactly three seconds, the lights illuminate the water. In those three seconds, Lee sees the submarine’s conning tower, black against moonlit water. Then the fishing boat turns, the lights sweep away, and darkness returns.

By the time Lee reaches the attack position, the submarine has dived. But Lee has seen enough. The problem isn’t power or weight or electrical engineering. The problem is duration. Flares burn for thirty seconds—long enough to warn the submarine. What he needs is three seconds of intense light, activated at the last possible moment.

Back at base, Lee sketches his first design on a napkin: a powerful carbon arc searchlight, twenty-four inches in diameter, mounted in a retractable housing beneath the aircraft. The pilot keeps it off during the entire radar approach, maintaining complete silence and darkness. Then, at exactly twenty feet altitude and fifty yards from the target, he flips a switch. Twenty-two million candlepower of light erupts from beneath the aircraft, turning night into day, freezing the submarine crew in perfect illumination, giving the bombardier precisely three seconds to drop depth charges before the U-boat can react. Three seconds. That’s all he needs.

The next morning, Lee requests a meeting with his commanding officer and explains his idea. The response is immediate and devastating. “That is completely illegal under current electrical specifications. Also physically impossible. Request denied.” Humphrey Lee does it anyway.

He has no official permission, no budget, and no engineering team. What he has is access to the Coastal Command Development Unit’s workshops and a grudging tolerance from mechanics who’ve seen too many good ideas die in committees. Lee starts with car headlamps, modified, rewired, and mounted on a wooden frame. Too weak. He moves to aircraft landing lights—brighter, but still inadequate.

He needs something that can illuminate a target from two hundred feet in total darkness. In March 1942, Lee finds it: a twenty-four-inch naval carbon arc searchlight designed for battleships, pulling power that would blow every fuse on a Wellington bomber. The RAF electrical engineers are right about one thing: his aircraft generator cannot power this monster. So Lee doesn’t use the generator. He designs a massive battery pack, connects it directly to the searchlight, and installs the entire assembly in a retractable housing that drops beneath the fuselage like a bomb.

The “Lee Light,” as other pilots mockingly call it, adds eight hundred pounds to the aircraft’s weight and reduces the bomb load by four depth charges. His commanding officer discovers the project in May 1942. The confrontation is nuclear. “You violated three separate Air Ministry directives. You’ve wasted ground resources. You’ve installed unauthorized equipment on operational aircraft. I should court-martial you.”

Lee stands at attention, maintaining perfect military bearing. “With respect, sir, I request permission to conduct one operational test. If it doesn’t work, I’ll personally dismantle every component at my own expense and accept any punishment you deem appropriate.” The commanding officer stares at him for a full ten seconds. “Then one test. You fail, you’re done. Clear?” “Yes, sir.”

On the night of June 3rd, 1942, Lee takes off from RAF Chivenor in Wellington ES986. His crew thinks this will be his last flight before reassignment to a desk job. His co-pilot, an Australian named Alan Triggs, has volunteered specifically to witness what he calls “Lee’s suicide mission.” The flight plan is simple: patrol the Bay of Biscay until radar picks up a submarine, then use the unauthorized searchlight for one attack run. Either the light works, or Lee’s career ends tonight.

At 2:17 a.m., the radar operator picks up a contact twelve miles ahead. Lee throttles back, begins his descent, approaches in total darkness. The submarine is running on the surface, recharging batteries, completely unaware that death is descending from above. Lee levels at fifty feet, lines up on the radar bearing. “Hold steady.” At two hundred yards, he can see nothing—just black water reflecting moonlight.

At one hundred yards, still nothing. His bombardier calls range over the intercom: “Seventy yards, sixty, fifty.” Lee reaches for the switch, and the night explodes into day. Twenty-two million candlepower of pure white light erupts from beneath the Wellington, turning the Bay of Biscay into a theater stage. There, frozen in perfect clarity, is the Italian submarine Luigi Torelli—crew scrambling on deck, conning tower gleaming, wake spreading white behind her.

Lee’s bombardier needs no instruction. The depth charges drop. Three seconds later, the light switches off. The submarine lives, but it’s crippled, unable to dive, captured by surface ships. The next morning, Lee radios base with four words: “The device functions perfectly.”

Two days later, Lee stands before a review board at Coastal Command headquarters. Present are his station commander, two Air Ministry engineers, a representative from the Admiralty, and Air Chief Marshal Philip Joubert de la Ferté, the newly appointed commander-in-chief of Coastal Command. The mood is hostile. The senior Air Ministry engineer opens the attack: “Squadron Leader Lee, your unauthorized modification violates section 7, paragraph 4 of Air Ministry Order 19416, which expressly forbids installation of non-standard electrical equipment exceeding generator capacity. You’ve bypassed safety systems, installed unapproved batteries, and created a significant fire hazard. This device should be immediately removed from service.”

Lee remains standing. “With respect, sir, the device successfully illuminated a submarine target and enabled an attack that damaged an enemy vessel.” The Admiralty representative cuts in: “Damaged, not sunk. You crippled an Italian submarine that was subsequently captured by surface ships. Congratulations. You’ve created an eight hundred pound weight penalty that reduces our bomb load to achieve something our destroyers could have accomplished anyway.” “Because I attacked with training depth charges,” Lee responds. “In operational configuration with full weapon load, the target would have been destroyed.”

The room erupts. Three officers begin shouting simultaneously. The station commander demands documentation. The engineers insist on three months of safety testing. The Admiralty representative questions the entire premise of night attacks. Lee stands at attention, saying nothing while his career burns around him.

Then Air Chief Marshal Joubert raises one hand. The room goes silent. Joubert has been commander-in-chief of Coastal Command for exactly eight days. He took command on June 5th, two days before Lee’s unauthorized mission. He’s a pragmatist who spent the last week reviewing statistics that make him physically ill. One submarine sunk in the Bay of Biscay in all of 1941. Meanwhile, U-boats are sinking sixty Allied ships per month.

Joubert looks directly at Lee. “How many submarines could you sink per month if I gave you ten aircraft equipped with this device?” Lee doesn’t hesitate. “Five, sir. Minimum.” The engineer nearly chokes. “That’s absurd. You’ve conducted exactly one test.” “Six?” Joubert interrupts. “I’d settle for six submarines if you could sink one per week.” He turns to his staff. “Gentlemen, I’ve reviewed Squadron Leader Lee’s service record: 1,500 hours of maritime patrol, two years in the development unit, zero disciplinary incidents until this one. He broke regulations because regulations were stopping him from winning the war. Now, you can spend three months testing his device while we lose another two hundred merchant ships, or you can install his searchlight on every available Wellington in 172 Squadron and see what happens. I choose option two.”

The room erupts again, but this time Joubert lets it. After thirty seconds, he stands. Everyone goes silent. “Squadron Leader Lee, you’re hereby promoted to Wing Commander and assigned to command 172 Squadron. You will equip your squadron with your searchlight device and conduct operational patrols beginning no later than July 1st. You will train your pilots personally. You will submit weekly kill reports directly to my office. You will prove your device works or you will accept full responsibility for wasting resources during wartime. Clear?” “Yes, sir.” “Dismissed.”

As Lee leaves the room, the Admiralty representative makes one final protest. “Sir, with respect, we’re basing operational doctrine on one partially successful test of unauthorized equipment designed by an officer with no engineering qualifications.” Joubert cuts him off. “Do you know what our current success rate is for night attacks on submarines? 0.3%. That’s not a doctrine. That’s statistical noise. Wing Commander Lee just gave us our first confirmed night attack in two years. I’ll take amateur hour over expert failure any day of the week.”

Before we see how Lee’s illegal searchlight changed the Battle of the Atlantic, a quick reminder: if you’re enjoying these stories of military mavericks who defied the experts and won wars, hit subscribe and turn on notifications. We release new Lastwords episodes every week, uncovering the untold stories of officers, engineers, and ordinary soldiers whose unauthorized innovations saved millions of lives. Now back to Wing Commander Lee and the night his invention started sinking.

172 Squadron receives its first Lee Light-equipped Wellington on June 15th, 1942. By July 1st, twelve aircraft carry the modification. None of the pilots believe it will work. Flight Lieutenant Norman Marrington voices what everyone’s thinking during the briefing: “So, we’re supposed to fly at fifty feet in darkness over open ocean and turn on a spotlight that weighs eight hundred pounds and might blind us if we look at it wrong. And this is somehow safer than dropping flares?”

Lee stands at the front of the briefing room, utterly calm. “The Lee Light activates for three seconds. In those three seconds, you will have perfect visual on a surfaced submarine at attack distance. Your bombardier will have a clear target. The U-boat crew will be frozen in shock, unable to man deck guns or reach the hatch. You will drop your depth charges and be gone before they recover. That’s the theory. Now we test it.”

The first kill comes faster than anyone expects. On July 5th, 1942, exactly one month after Lee’s first test, Pilot Officer Wiley B. Howell takes off from RAF Chivenor on a routine night patrol. Howell is an American volunteer, twenty-two years old, flying his eighth mission with 172 Squadron. He’s never used the Lee Light in combat.

At 11:34 p.m., his radar operator picks up a contact—U-502, a Type VIIC submarine commanded by Kapitänleutnant Jürgen von Rosenstiel, returning from a successful patrol in the Caribbean. The submarine is running on the surface, making seventeen knots, confident that darkness provides safety. Howell begins his approach exactly as Lee taught him: throttle back, slow descent, maintain absolute radio silence. At three miles, he can see nothing—just darkness and moonlight reflecting on waves.

At one mile, still nothing. At two hundred yards, his navigator calls out, “Target should be dead ahead.” Howell sees only water. At fifty yards, he flips the switch. The Lee Light transforms night into noon. There, frozen in perfect illumination, is U-502—deck crew scrambling, officers diving for the hatch, wake spreading white.

Howell’s bombardier doesn’t need instructions. Six depth charges drop in perfect stick, bracketing the submarine’s pressure hull. Three seconds later, the light switches off. Howell banks hard right, climbing, already turning for home. Behind him, U-502 breaks in half and sinks in under two minutes. All fifty-two crew members die. None survive long enough to send a distress signal.

The next morning, Howell lands at Chivenor and files a report that changes history. “Submarine illuminated at 37 hours. Attacked with depth charges. Target destroyed. Requests permission for additional patrols.” Lee reads the report three times, then walks to Joubert’s office and places it on his desk without comment. Joubert reads it once, then picks up his phone and calls the Air Ministry. “This is Joubert. I want Lee Lights installed on every Wellington in Coastal Command. Not next month. Now.”

The kills accelerate. July 7th: Squadron Leader Jefferson Greswell, Lee’s own co-pilot from the first test, illuminates and attacks U-159. Damaged beyond repair, the submarine limps to port and never returns to sea. July 13th: U-751 caught recharging on the surface, sunk in one attack. July 16th: U-335 destroyed in the Bay of Biscay. No survivors.

By August, RAF Coastal Command is sinking more submarines in the Bay of Biscay than in the previous twelve months combined. U-boat commanders stop surfacing at night. Admiral Dönitz issues emergency orders: all boats will recharge batteries during daylight hours only. Night surface operations are suspended until further notice. But daylight operations mean RAF fighters, radar-equipped ships, and convoys with air cover. The U-boats are trapped—surface at night and face the Lee Light, surface by day and face everything else.

The statistics tell the story. In the five months before the Lee Light becomes operational, RAF Coastal Command sinks seven submarines in the Bay of Biscay. In the five months after, they sink forty-one. The success rate jumps from 0.3% to 40%—a hundredfold increase from one modification designed by one officer with no engineering degree.

On the night of June 7th to 8th, 1944, Flying Officer Kenneth Owen Moore takes the Lee Light technology to its ultimate expression. Moore is a twenty-two-year-old Canadian flying a B-24 Liberator from RAF Saint-Eval on D-Day plus one. His mission: patrol the approaches to the English Channel and prevent U-boats from attacking the Normandy invasion fleet. At 21:17 a.m., Moore’s radar detects a submarine. He approaches in total darkness, activates the Lee Light at fifty yards, illuminates U-441, and drops six depth charges. The submarine sinks in ninety seconds.

Moore turns for home. Then, at 2:39 a.m., exactly twenty-two minutes later, his radar detects a second submarine. He repeats the approach, activates the light. U-413 explodes in a fireball visible from twenty miles away. Moore lands at Saint-Eval with this entry in his combat log: “Sighted two subs. Sank same.” For this mission, Moore receives the Distinguished Service Order and the American Silver Star. His gunners and navigator receive Distinguished Flying Crosses. The Liberator receives a fresh coat of paint and a new nickname: Killer Moore.

If you’re amazed by how one man’s unauthorized invention turned the Battle of the Atlantic, you need to watch our episode on Percy Hobart, the general who designed the D-Day tanks that Churchill called impossible and Eisenhower called essential. Link in the description. And if you want to support this channel and help us tell more stories like this, check out our Patreon link below.

Now, the final chapter: what happened to Humphrey Lee after the war. By the end of World War II, Lee Lights have been installed on 1,800 aircraft across RAF Coastal Command, Royal Canadian Air Force squadrons, and US Navy patrol bombers. The device directly contributes to the sinking of 212 U-boats—more than one quarter of all German submarines lost in the Atlantic.

Admiral Karl Dönitz later writes in his memoirs, “The introduction of the searchlight aircraft made it impossible to operate effectively at night. This single weapon, more than any other, forced us to abandon our Wolfpack tactics and cost us the Battle of the Atlantic.” In 1943, a U-boat commander captured after his submarine was illuminated and destroyed by a Lee Light tells his interrogators, “We called it Das Totenlicht—the light of death. You would be running on the surface, confident in the darkness, and then God himself would flip a switch and turn you into a target. It lasted three seconds. That was enough.”

The technology saves an estimated 400,000 Allied sailors and merchant seamen. Humphrey Lee receives no public recognition during the war; his invention remains classified until 1946. When the war ends, he continues serving in the RAF, eventually retiring as an Air Commodore in 1962. He refuses every interview request, declines every invitation to speak at military conferences. When the RAF Museum asks permission to display his original workshop prototype, he writes back, “The device worked because good men flew it. Tell their stories, not mine.”

Lee dies on November 19th, 2000, at age eighty-three. His obituary in The Times runs four paragraphs, mostly about his administrative service in the 1950s. The Lee Light gets one sentence. But in 2008, the RAF finally installs a permanent exhibition about the Lee Light at the RAF Museum in Hendon. The centerpiece is Lee’s original workshop prototype—the jury-rigged searchlight built from car parts and salvaged landing lights, held together with wire and hope. Beneath it, a plaque reads: “Designed in violation of regulations, built without authorization, installed against direct orders. Saved 400,000 lives.”

Wiley B. Howell, the young American who got the first Lee Light kill, later becomes Captain Howell, commanding the aircraft carrier USS Bennington. In 1965, at a reunion of 172 Squadron survivors, he meets an aging Wing Commander Lee and says, “Sir, because of you, I lived long enough to get married. So did three hundred other pilots. We owe you everything.” Lee smiles and shakes his head. “You owe yourselves everything. I just gave you a better flashlight.”

The lesson isn’t subtle. Humphrey Lee didn’t have an engineering degree, didn’t have official authorization, didn’t have expert consensus. What he had was a problem that needed solving and the courage to ignore everyone who said it couldn’t be done. The experts were wrong. The regulations were wrong. The established doctrine was wrong. And a middle-aged squadron leader with a car headlight and a dream was right.

Sometimes the most important words in military history aren’t “yes, sir” or “following orders.” Sometimes they’re, “Watch this.”