A relic from a legendary wartime commando raid by British forces in 1942 discovered eight decades later now enjoys pride of place in a French museum.

Rusty, burned, slightly bent and buckled, and perforated by the German shells which struck it on March 28, 1942, a door from the superstructure of HMS Campbeltown has been partially restored and cleaned and can now be seen in an exhibition championing the deeds of those who attacked the docks at St Nazaire.

In March 1942, HMS Campbeltown, the former American flush deck cruiser USS Buchanan, acquired by the Royal Navy, took part in the famous and heroic raid named Operation Chariot on the French port of St Nazaire. The aim of the raid was to deny the German capital ships such as the Tirpitz, the use of the huge Normandie drydock, named after the famous French ocean liner.

Operation Chariot began in Falmouth from where Campbeltown, HM ships Atherstone and Tynedale accompanied by MTB's, ML's and 16 motor boats sailed for France carrying 159 officers and men of 2 Company Commando and a Special Services brigade.

Supported by a flotilla of smaller craft and commando raiders who caused havoc ashore, veteran destroyer Campbeltown rammed the dock gates at speed. The crew opened all the sea cocks allowing the ship to settle.

Expertly concealed deep in her bows the warship carried four tons of high explosive (24 depth charges) timed to detonate some hours after the German soldiers had searched the ship for explosive charges. Campbeltown later blew up, destroying the dock gates which remained inoperable for the rest of the war.

Pretty much nothing remained of the forward section of the destroyer; the blast caused a tidal wave which swept through the dock, the caisson was wrecked, several hundred Germans were killed instantly and the dock put out of action till after the war.

Falmouth Packet: HMS Campbeltown embedded in the docks gateHMS Campbeltown embedded in the docks gate (Image: Royal Navy)

Fast forward nearly eight decades and while ‘the greatest raid of all’ entered naval history with memorials and commemorative events on both sides of the Channel, workers upgrading the port facilities in St Nazaire unearthed a bulkhead door around 100 metres from the Joubert/Normandie Dock which HMS Campbeltown attacked.

It was put in storage while its origin was determined and a possible home was found for it.

Thanks to brothers Marc and Luc Braeuer, who run a museum in a former German bunker, and retired British Army officer Matt Minshall, a fitting home was found after the door was identified as coming from the destroyer.

The door was unveiled by sailors from patrol boats HM ships Archer and Example, which have spent several weeks this spring operating along the French Atlantic coast.

Once cleaned, still legible on the door is the wording: "DOOR NO.6. COLLISION. CLOSE AND DOG [CLIP] IMMEDIATELY."

Museum director Marc Braeuer said the survival of the door was a “fascinating story”.

He continued: “It was preserved by one of the port's managers, who put it in storage pending a decision.

“We naturally stepped in to restore and display this historic vestige in its rightful place. We worked with Mr Minshall, who put together a team of history buffs to save this relic. The work bore fruit, and after historical research, the door was indeed identified as part of the glorious ship.”

Lieutenant Oliver Thomas, HMS Example’s Commanding Officer, said the two P2000s’ week-long visit to the Loire port had been packed with memorable occasions – and above all warmth from their hosts.

“It proved to be a very special week. We were thoroughly welcomed by the town of Saint Nazaire, St Nazaire society and Musée Le Grand Blockhaus.

“It was an honour and a privilege for us to represent the Royal Navy in commemorating Operation Chariot, remembering those who achieved the impossible, honouring the incredible bravery and sacrifice of sailors and soldiers.”

The door, as well as a wider display on Operation Chariot, can be seen at the Musée le Grand Blockhaus in Batz-sur-Mer, a dozen miles west of St Nazaire, where there are also displays on the sinking of the troopship Lancastria – lost off St Nazaire in June 1940 and the worst disaster in British maritime history – and events in and around the French port in World War Two.

HMS Campbeltown was commanded by Lt Commander Stephen Beattie, who was awarded the VC for his bravery. He died at Mullion in 1975 and is buried at Ruan Minor churchyard.

Five VC’s were awarded for this raid. Able Seaman William Savage - awarded a posthumous VC for the part he played - is buried in Falmouth cemetery.

Of the 611 commandos and sailors who took part in Operation Chariot, 169 were killed and 200, mostly wounded, were taken prisoner. Only 242 returned to Falmouth after the raid.

A fitting memorial to those who took part in the raid now exists on the Prince of Wales Pier, Falmouth and was unveiled by the then Duke and Duchess of Cornwall on July 11, 2008.