John Lorimer, a reserve seaman, was “young, 19 and stupid” when in 1943 he volunteered for a “special and hazardous duty”. According to the advert, participants “must be able to swim”. He found himself on a mission from which he was not expected to return.

The objective of Operation Source was to use previously untried midget submarines (known as X-craft) to neutralise German warships in the waters of northern Norway. Among the targets was the heavily armed and seemingly invincible battleship Tirpitz, which had been posing a significant threat to the Arctic convoys. Winston Churchill had made her destruction a top priority. “She is the beast that would eat us,” he had declared in 1941. “If she were only crippled, the entire naval situation throughout the world would be altered.” It was easier said than done.

To Sweden on Foot

Lorimer found himself on an arduous training programme. Not only did he and his colleagues have to operate their four-man 52ft X-craft, which was powered by a modified London bus engine, they also had to learn to dive and to practise walking long distances, in case they had to make their way on foot from occupied Norway to neutral Sweden.

Easier said than done: the Fleet Air Arm prepares for the attack on the Tirpitz, April 1944.

He recalled watching the prototype of the X-craft being built in an old tin shed. “It was awful,” he told the Daily Mail in 2007. “I thought, ‘This is never going to work. It’ll be a glorious cock-up.’ ” On one occasion he almost drowned in Loch Striven when he discovered, somewhat belatedly, that the X-craft’s hatch had not sealed properly; he had to endure an agonising 40-minute wait in pitch darkness with the air running out before being rescued.

“It was awful. I thought, ‘This is never going to work. It’ll be a glorious cock-up.’ ”

“There was an awful lot we didn’t know, such as the dangers of diving to 100ft with pure oxygen, which kills you in half a minute,” he told James Delingpole in The Daily Telegraph in 2008 on the 65th anniversary of the raid. “This all had to be discovered by experimentation, and there were casualties. But that’s war.”

The operation began on September 11, 1943. Six large submarines, each with an X-craft in tow, slipped out of Loch Cairnbawn, on the northwest coast of Scotland, heading for the Norwegian fjords. X5, X6 and X7 were heading for the Tirpitz, while X8 would attack the Lützow, and X9 and X10 would go for the Scharnhorst. Lorimer was in X6 (known informally as Piker II).

Lost at Sea

En route X8 was crippled by mechanical failure, while X9 and her crew were lost at sea. After ten days X6 slipped into Kaafjord in northern Norway and Lorimer had his first sighting of the Tirpitz. “It was surreal … lit up like a Christmas tree,” he said. “My first thought was that she was so pretty, it seemed an awful shame to have to blow her up.”

Hitler at the launching of the battleship Tirpitz, in Wilhelmshaven.

On board each of the X-craft was a specialist diver trained to cut through the thick steel underwater netting that surrounded the Tirpitz. However, Donald Cameron, the X6 commander, spotted through his leaking periscope a trawler bringing German sailors back from shore leave and audaciously followed it through a gate in the netting. “We could see the sailors’ faces quite clearly, but they were too pissed to notice us,” Lorimer told Delingpole.

“My first thought was that she was so pretty, it seemed an awful shame to have to blow her up.”

The next morning they pulled off a similar trick through an inner ring of netting, but then disaster struck. “We hit an uncharted rock,” Lorimer said. “Our periscope caught fire. The boat broke surface at 45 degrees.” Their compass was also broken. “We had no idea where bloody north was,” he added. Cameron managed to dive again, but X6 was now filled with fumes and almost uncontrollable. They dropped their Amatol explosives under the Tirpitz’s keel, rammed the vessel and then surfaced to be greeted by a hail of bullets. All the crew of X6 were captured and taken aboard the Tirpitz without getting their feet wet. Lorimer even joked to Cameron that they should salute the German flag.

The Tirpitz in what is believed to be a Norwegian fjord.

They were now on a ship that was about to be blown up not only by their explosives, but also those from X7 (X5 and her crew had also been lost). They tried in vain to warn their captors, but the Germans were more interested in preparing them for a firing squad. “Only the intervention of a senior German officer prevented us from being shot,” Lorimer recalled. “I always meant to write and thank him, but never did learn his name.”

Lorimer was below decks being interrogated when the British explosives lifted the Tirpitz 70ft out of the water. “This Jerry is writing down my details,” he recalled. “I believe we had just got to my date of birth when the whole bloody thing blew. He went one way and I went the other. I’ll never forget his face.”

There was uproar. “The Germans were very hostile, and I wouldn’t blame them,” Lorimer said with typical understatement.” Nevertheless, a German admiral insisted that the prisoners should still be well treated. Lorimer’s abiding memory, however, was “being bloody furious that the ship was still floating”. Although the Tirpitz did not sink, she never again saw useful service and was eventually sunk in 1944 by RAF Lancaster bombers with the loss of about 1,000 German lives.

“The whole bloody thing blew. He went one way and I went the other. I’ll never forget his face.”

Lorimer spent more than 18 months in the Marlag und Milag Nord prisoner-of-war camp near Bremen, where the ablution block was outside the camp perimeter. The prisoners would be marched there and back, but they soon realised that their bored captors were only counting the number of feet, not people. They created a mannequin that was smuggled out in pieces and then “marched” back into the camp while one of their number remained in the block and later escaped, a story told in the film Albert R.N. (1953) starring Jack Warner. Lorimer was also involved in digging an escape tunnel, but it flooded and he remained a prisoner until May 1945, when he returned to his native Scotland.

The official report on Operation Source declared that the attack on the Tirpitz “will surely go down in history as one of the most courageous acts of all time”. Cameron and Godfrey Place (X7), the surviving commanding officers of the X-craft, were awarded the Victoria Cross, while Lorimer was among three crew members who received the Distinguished Service Order. Pinning the insignia on him at Buckingham Palace, George VI was heard to say: “Good show! Good show!”

Worked in Timber

John Thornton Lorimer was born in Kelso in the Scottish Borders, the youngest of four children of James Lorimer, a doctor, and his wife, Hilda. His elder siblings were Hamish, who joined the RAF, Dorothy, and George, who served with the Gurkhas. He was educated at the Imperial Service College (now Haileybury), joining the navy at 18 as a rating before being commissioned. After the war he played rugby for the navy against the All Blacks, but his team were thrashed.

Back in civilian life Lorimer took a BSc in forestry at the University of Edinburgh and worked in timber import and export. Later he became a forestry consultant, continuing to work into his eighties.

Lorimer, second from left, at Buckingham Palace in 1945 for an investiture ceremony with other X-craft crew.

He met Judith Hughes-Onslow, a Wren, while training for Operation Source and they became engaged. For six months she did not know if he was dead or alive until one day a colleague read a signal saying that he was safe. Almost immediately upon his return in 1945 they were married, later settling in Kirkmichael, a village in Ayrshire. They had a son, Patrick, who is an architect and deputy lord-lieutenant for Ayrshire and Arran, and a daughter, Bridget, who has recently retired after a career that ranged from being a nanny to a spell as a driving instructor. When her children grew older, Judith worked for Schwartz, the spice maker. She died in 2011 and Lorimer is survived by their children, three grandchildren and six great-grandchildren.

Cheerful and Irreverent

Operation Source was depicted in the film Above Us the Waves (1955), directed by Ralph Thomas and starring John Mills and Donald Sinden, to whom Lorimer lent the pipe that had accompanied him on the original mission (“A bloody awful film, by the way,” Lorimer said). In 2005 he was at a party in London where Sinden was one of the guests. “When he found out who I was, he came up and hugged me.”

John Lorimer: “One was merely doing one’s duty.”

Twenty years after the raid Lorimer was invited to a reunion with the surviving crew of the Tirpitz, after which he commented: “I really like the Germans, they are very nice.”

His nephew John Fergusson told the BBC: “He was always a bit of a hero because of what he did, but he did not speak about it unless he was asked.”

Looking back on Operation Source, Lorimer remained cheerful and irreverent. “Everyone thinks one was frightfully brave, but it’s all bullshit,” he said. “One was merely doing one’s duty.”

John Lorimer, D.S.O., wartime naval officer, was born on July 9, 1922. He died, after a short illness, on December 1, 2019, aged 97