It was Rupert Lonsdale's thirty-fifth birthday, and a German pilot was telling him to swim. Behind him his submarine wallowed with a hole in her stern, no rudder, no engines, both machine guns jammed and a white messroom tablecloth flying from the mast. HMS Seal had spent the previous seven hours pinned to the floor of the Kattegat with her crew slowly suffocating. On 5 May 1940 she became the only Royal Navy submarine the Germans captured at sea in the whole war, and Lonsdale the only British captain to surrender his ship.
Seal was one of six Grampus-class minelayers, big boats at 1,810 tons on the surface and 293 feet long, laid down at Chatham in 1936 and commissioned in May 1939 — days before HMS Thetis was lost on trials off Liverpool, taking a good many of her crew's friends with her. She got as far as Aden, bound for China, before war broke out, then spent the winter on North Sea patrols. Admiral Horton, meeting her at Rosyth, complained she was too damn clean for a wartime boat; having read her logs, he revised that into a compliment about her crew. Operation DF 7 then sent her into the Kattegat, the shallow strait between Denmark and Sweden, to lay fifty mines — an unreasonable task for a boat her size. She sailed from Immingham on 29 April 1940.
A Heinkel float plane found her before dawn on 4 May and put a bomb close enough to hurt. Trawlers were working her primary target area, so she laid her mines elsewhere, finishing at about a quarter to ten, and turned for home with the trawlers behind her and, by mid-afternoon, nine motor torpedo boats closing from another direction. Too many hours of daylight were left and there was nowhere deep to hide. Lonsdale zig-zagged until evening, then settled on the seabed to wait for dark.
He had put her down in an uncharted minefield. A hydroplane snagged a mooring cable and the current walked the mine onto her stern. The explosion drove water into the after compartments and tilted her ten degrees bow-up; astonishingly, the ships hunting her heard nothing and moved off. Three attempts to surface failed. The eleven-ton drop keel went — which meant that even if she rose she could never dive again — and still she would not come up. At ten past one in the morning, with the air going bad, Lonsdale called his crew to prayer and led them in the Lord's Prayer, then had them crawl forward to shift her balance; many fainted or were sick. Then an engineer remembered one last air group with a little pressure in it, climbed to the valve and opened it, and Seal began to move.
She broke surface at half past one. The rush of clean air gave the crew blinding headaches. Lonsdale ditched the confidential books, smashed the Asdic, and signalled the Admiralty: Am making for the Swedish coast. Two replies came back, one telling him the safety of his people came first — and with the cipher books gone he could read neither, which cost him years of doubt about what he did next.
The rudder was wrecked and she would only run astern; then mud in the lubricating system seized her one working engine. At half past two, two Arado seaplanes and a Heinkel came in, the Lewis guns jammed, men were wounded, and Lonsdale hoisted the tablecloth. A trawler took the crew off at half past six, attempts to scuttle her failed, and Seal was towed into Frederikshavn. Her mines, meanwhile, were doing their work: between 5 May and 5 June they sank a German freighter, three Swedish ships and a Danish sailing vessel.
The Germans did get something real out of her. British torpedo contact pistols turned out to be better than their own, and the design went into German service — a fix for a fault that had been costing U-boats their kills. The submarine herself was a disappointment. Admiral Rolf Carls insisted she be made operational even though three new U-boats could be built for the cost, and she was commissioned as UB under Fregattenkapitän Bruno Mahn, at fifty-two the oldest German submarine commander of the war. Her equipment was wholly incompatible with German systems, and Krupp did not finish fabricating a replacement until late 1942. She never made a patrol. She served as a training boat and a propaganda exhibit, and by mid-1943 she was paid off, stripped, and left in a corner of the Kiel dockyard. On 3 May 1945 — the same day the Cap Arcona burned down the coast in Lübeck Bay — UB was scuttled in Heikendorf Bay.
Everyone aboard survived except two. Able Seaman Smith went overboard when she surfaced. Petty Officer Barnes broke out of Stalag XX A at Toruń with a British sergeant-major, reached the Polish underground and crossed into Soviet territory, where the border guards separated the two men, told them to run, and opened fire. Barnes was killed; his companion ended up in Butyrka prison in Moscow.
Others did better. Don "Tubby" Lister and Wally Hammond, an engine room artificer off the sunken Shark, talked their way out of Colditz on the grounds that they were not officers, escaped from the easier camp they were sent to, and walked several hundred miles to Switzerland. Lieutenant Trevor Beet, left aboard when Lonsdale swam away, finished the war in Colditz after three failed attempts. Lonsdale and Beet were court-martialled in 1946 and honourably acquitted.
54.3667°N, 10.1833°E — Heikendorf Bay, on the eastern shore of the Kieler Förde about 6 km north-east of Kiel city centre, where UB was scuttled on 3 May 1945. Nothing is visible; the wreck was broken up. Fly the fjord at 1,500–2,500 ft and the geography does the explaining: Kiel's naval basins and the ThyssenKrupp submarine yards to the south-west, Laboe with its naval memorial tower and the museum U-boat U-995 at the fjord mouth to the north, the Kiel Canal locks at Holtenau on the west bank. Kiel-Holtenau (EDHK) is 5 km west; Hamburg (EDDH) 90 km south, Lübeck (EDHL) 60 km south-east. Expect heavy small-craft and ferry traffic on the fjord in summer, and Baltic sea fog in spring.