Operation Tracer: Six Men Sealed Inside the Rock

25 June 2026 Last checked 2026-06-25

Six men volunteered to be sealed inside the Rock of Gibraltar to spy on the enemy if it fell. The true story of Operation Tracer and the Stay Behind Cave.

Six men agreed to be sealed alive inside the Rock of Gibraltar. Volunteers, every one. If the fortress fell to Hitler they would be walled into a chamber roughly 45 feet long, 1,350 feet up inside the limestone, with stores for up to seven years and no way out. Their job was to watch the Strait through a slit in the cliff and radio what they saw while German troops walked overhead.

The wall was built. The provisions were stacked. Then the war turned, and on 24 August 1943 the Director of Naval Intelligence ordered a final wireless exercise, the stores shared out and the entrance sealed. The room slipped out of memory so completely that when cavers found it again in the 1990s, nobody in Gibraltar could say for certain what it was.

The nightmare that started it

In 1940 Nazi Germany drew up Operation Felix, a plan to march through Spain, take Gibraltar and slam shut the western gate of the Mediterranean. For Britain the prospect was unbearable. Lose the Rock and you lose your eyes on the Strait, the 13 kilometre channel every ship between the Atlantic and the Mediterranean must pass through. London needed a way to keep watching even after the fortress was gone.

The answer came in 1941 from Rear Admiral John Henry Godfrey, Director of Naval Intelligence and the man usually credited with inspiring Ian Fleming's M. Fleming was not a bystander: he served as Godfrey's personal assistant and, as the Operation Tracer record sets out, was involved in the scheme. Some of the planning meetings were held at Godfrey's house in Mayfair rather than in Whitehall, which tells you how closely it was held.

The doctor who had already lived in a cave

To make the unthinkable survivable, the Admiralty recalled a man who had done something like it. Surgeon Commander George Murray Levick had sailed with Scott's Terra Nova expedition as surgeon and zoologist. In February 1912, cut off from the ship by pack ice, Levick and the five other men of the Northern Party dug into a snow bank on Inexpressible Island and spent the winter in a cave measuring about 12 feet by 9 feet, too low to stand up in. They came out alive.

So the Admiralty had, in one retired officer, the only relevant expertise in Britain. Levick recruited the two doctors, then advised on psychological screening to pick men who would not crack, on ventilation and sanitation, on diet and exercise, and on what to do with a body. His own winter had taught him the thing the engineers kept missing. Boredom and despair kill as efficiently as cold.

The man who designed life inside a 45 foot chamber had himself survived a polar winter in one measuring 12 feet by 9. That is not a coincidence of casting. It is the reason he was chosen.

The room in the rock

The hide was cut into the tunnels behind Lord Airey's Battery, high in what is now the Upper Rock Nature Reserve. Published accounts of the living chamber differ. The Naval Intelligence figures give 45 feet by 16 feet by 8 feet, about 163 cubic metres, at an elevation of 1,350 feet. The Gibraltar National Museum's own description of the main chamber puts it at roughly 18 metres by 5.5 metres, which is longer and a little narrower. We have not found a survey that reconciles the two, so treat both as approximate.

The museum's account is the most detailed one published, and the domestic particulars are what make it land. The floor was laid with cork tiles for sound insulation, so that nothing could be heard through the rock. A sink and tap stood at the far right of the chamber, fed by a metal water tank behind the southern wall holding 10,000 imperial gallons. A corridor ran to a flight of stairs and two further rooms: one with two toilets, one fitted out as a radio shack.

There was no front door. A tunnel running west ended at a small observation post where a slit just 15 centimetres by 1.5 centimetres had been cut through the western wall, and through that letterbox most of the Bay of Gibraltar was visible. The stairs led the other way, to a natural opening in the east face giving onto a small platform on the cliffs, with the coastline running away toward Malaga. Earlier retellings of this story, including an earlier version of this page, described two observation slits ventilating the chamber. The museum's survey does not support that, and the ventilation came from machinery.

Power from a bicycle and a leather strap

Electricity came from human legs. A bicycle was rigged to drive a generator and the ventilation plant, and its chain was swapped for a leather strap so the mechanism would run quietly. A hand cranked generator was provided as a second source. Between them they charged three small 12 volt batteries, and a radio aerial was improvised from an 18 foot rod that could be pushed out through one of the openings. Colonel Gambier-Parry, the MI6 radio specialist, ran the transmission trials from January 1942, as the technical reconstruction of the Tracer radio station records.

Six volunteers and a one way wall

The team was small and deliberately balanced: an executive officer to lead, two medical men to keep everyone alive, and three wireless operators to send the sighting reports. The original leader was replaced before the operation was ready, and an officer remembered as "Windy" Gale took the post. A Lieutenant White was announced to the team in March 1942. The doctors were Bruce Cooper and Arthur Milner, whose surname appears as Milne in some accounts.

Cooper was a young Royal Naval Volunteer Reserve surgeon recruited while on shore leave, and he arrived in Gibraltar aboard HMS Cormorant in the summer of 1942. He would become the human face of the whole affair, the one man who lived long enough to walk back into the chamber and say out loud what it had been built for.

The planners followed the logic all the way down. A report in January 1942 recommended that any member of the team who died inside should be embalmed and then cemented into the structure, because there would be no way to carry a body out and no possibility of burial. The six knew this when they volunteered. They also knew that if they ever did come out, it might be into a Gibraltar under occupation, with nobody coming for them.

Why it never happened

History spared them. Hitler never launched Operation Felix, Spain stayed neutral, and the Allied advances in North Africa and Sicily through 1943 pushed the threat to Gibraltar off the table. The observation post was finished, stocked and manned by men who had been living with the prospect for a year, and then it was simply not needed.

The order to wind it up came on 24 August 1943. The volunteers were stood down, the stores were distributed around the garrison, the chambers were sealed, and every man went back to an ordinary war bound by an oath of silence he kept. For decades the only trace was rumour. Older Gibraltarians talked about a sealed room somewhere on the upper ridges, full of supplies, and nobody could prove it.

The breakthrough behind the corrugated iron

It surfaced through patient and slightly obsessive exploration. Members of the Gibraltar Caving Group, working the tunnel system near Lord Airey's Battery, noticed a draught of air where there should not have been one. Moving air means an opening, and an opening means a space beyond. Behind a sheet of corrugated iron they found a bricked up wall, and behind the wall the chambers, matching the rumours point for point.

On the date of that breakthrough the published record is genuinely untidy, and it is worth being straight about it. The Government of Gibraltar's heritage listing and most secondary accounts say 1997. Other passages in the same sources say late 1996, and the Gibraltar National Museum's own page gives no year at all, saying only that the wall was found in the 1990s. An earlier version of this post stated 1996 as fact. It is not established, so we are not going to pretend otherwise.

Confirmation came first from the men who built it rather than the men who would have lived in it. In September 1998 Dennis Woods, one of the builders, visited the site and identified it. He also supplied the name the work had gone by at the time: Braithwaite's Cave, after Major J. A. Braithwaite, killed in a tunnelling explosion during the war.

Bruce Cooper comes home

The proof that mattered came from the last survivor. In October 2008, in his nineties, Bruce Cooper returned to Gibraltar and was taken back into the chamber. He confirmed that this was the hide where he and five others would have been sealed in to watch the enemy had the Rock fallen. The visit was arranged by the documentary producer Martin Nuza with help from the Gibraltar researcher Jim Crone.

Cooper died on 3 December 2010, aged 96, shortly after his birthday and the last of the six. With his confirmation, Operation Tracer passed out of rumour and into the documented history of the Second World War.

To stand in the chamber with the last survivor closed a loop that had stayed open for more than sixty years. That was the moment a Gibraltar legend became a Gibraltar fact.

What is still not known

Three things remain open, and a post that pretended otherwise would be worth less than this one. The Manual of Operation Tracer, which would have set out the codes, procedures and full equipment list, has never been found. The surviving Naval Intelligence paperwork sits in the Admiralty files at the National Archives at Kew, and it is a summary rather than the operational detail.

There is also a loose end that circulates online and should be labelled for what it is. Cooper's recollection of the chamber he was shown in 1942 is said by some accounts to differ from the layout of the complex found in the 1990s, which has fed a theory that a second hide exists somewhere in the Rock. We have seen that claim only in forum and enthusiast postings, never in a government or museum source. Treat it as unverified. If you want the authoritative position, the Gibraltar National Museum is the body to ask.

Seeing the secret Rock for yourself

The Stay Behind Cave complex is a protected heritage site, not a walk in attraction. Access is controlled and arrangements change, so check with the Gibraltar National Museum or the Ministry for Heritage before you plan a trip around it rather than turning up at Lord Airey's Battery hoping. Our Rock of Gibraltar guide covers the nature reserve, its entrances and the walking routes.

One piece of planning has changed and it catches people out. The cable car is shut. The official Upper Rock information says it is undergoing full refurbishment and is expected to reopen in 2027, and the operator MH Bland describes an entire rebuild of the complex taking hourly capacity from 260 passengers to 1,150. Neither publishes the date it actually stopped running, so we are not going to quote one. Until it returns the Upper Rock is reached on foot or by licensed minibus taxi tour, which is a longer day than most visitors budget for. Plan the climb, or book the taxi.

The rest of the hollow Rock is open and it is the real reason to give this place more than a morning. The Great Siege Tunnels and Sergeant Major Ince's story show where the habit of digging began, 160 years before Tracer. Lower St Michael's Cave and its underground lake show what the limestone did on its own. And the story of the wartime evacuation explains why there were so few civilians on the Rock while the Tracer chamber was being cut.

Make the Rock your base, not a day trip

Operation Tracer rewards the kind of traveller who wants the story behind the story rather than a photograph and a queue. That takes two days on the Rock, not four hours off a coach. Victory Suites is set up for it. We are on Devils Tower Road, a flat ten minute walk from Grand Casemates Square and minutes from the airport and the frontier, with more than 100 serviced apartments, full kitchens, an indoor pool and rates quoted in GBP. Book a couple of nights, walk up to Lord Airey's Battery, and give the Rock's secrets the time they are owed.