The large minelaying submarine HMS Seal, which had featured in a recent Newsreel, was sent to the Kattegat to lay mines between Sweden and Germany. In the early hours of 4th May she was spotted by aircraft and forced to dive. Unable to surface again until nightfall, at around 7pm she was shaken by a huge explosion, having hit a mine. Two ratings just managed to escape from the flooded rear compartments before the watertight doors were sealed. The seriously damaged submarine now lay with her aft end wedged in the mud unable to surface, despite frantic efforts from the crew.
After nearly 24 hours submerged the whole crew were seriously affected by lack of oxygen and some were nearly comatose. Lieut.Commander Rupert Lonsdale, a religious man, led his men in the Lords Prayer in the control room. Lieutenant Beet was later to describe how they were all panting for breath without any exertion and that he had to fight to keep awake. With the submarine lying at an angle of 30 degrees Lonsdale now had the idea to rig up a line so that all the men could climb to the forward end of the craft. His prayers were answered when HMS Seal suddenly rose to the surface. It was now around 1.30am on the 5th May. The entire crew were suffering severe headaches and nausea as they readjusted to normal levels of oxygen. The submarines steering was badly damaged. An attempt was made to head for Sweden although HMS Seal was pointed in the wrong direction and would not turn.
They were virtually a sitting duck on the surface when they were attacked by German planes. The First Officer, Lieut. Commander Butler was shot in the leg and collapsed from loss of blood. Lonsdale then took to the Lewis Guns and took on the attacking planes until the guns jammed. Eventually he was persuaded to wave the white wardroom table cloth in surrender. The Germans insisted that he swim over to a flying boat to surrender in person. Having ensured that the Asdic equipment was destroyed along with confidential documents, Lonsdale believed that HMS Seal was sinking. The crew, who were shortly afterwards taken off by boat, also believed that she was sinking. Lonsdale was mortified when he learnt otherwise:
I do not expect ever to forget the shock which I experienced a few days after my capture when out for a walk under guard at Kiel, I saw the Seal being towed into port; nor, almost worse, when on leaving Kiel for the prison camp I caught sight of her in dry dock.
It was the only British vessel to be surrendered and captured during the war. A propaganda triumph for the Germans, they were unable to make use of the Seal themselves despite their efforts to make her serviceable.
After five years in captivity Lonsdale returned to to face a Court Martial. The Admiralty decided that Kings regulations applied and that he should not be “denied the chance” of clearing himself of “the stigma of surrendering his ship to the enemy”.
After the court had heard from many of Seal’s crew, Lonsdale was honourably discharged. He was later ordained in the Church of England.