I have carried out no detailed research on those Deadlight boats the subject of initial unsuccessful tows to destruction, and I doubt if anyone else has.

A quick trawl through my notes indicates that U-294, U541, U-1010 and U-2506 (twice !) were each returned to Lough Foyle when their tows parted, and were shortly thereafter towed out and destroyed succesfully.

It seems to have been the policy, with the Loch Ryan destructions, for boats not to be retrieved following a failed tow; they seem to have been sunk by gunfire where they languished in those cases where the boats did not immediately disappear under the surface. Though in one case only - U-1110 - it may have been returned to base and the exercise repeated when the tow had been adequately re-established.

116 U-boats were destroyed under Deadlight though fewer than half this number reached the specified scuttling point. Only two were despatched by the preferred method of electrically-fired or delayed action explosive charges; seven were successfully sunk by British submarine attack; thirteen were sunk after RAF or FAA aircraft attack; the remainder foundered during the towing operation prior to reaching the designated sctuttling point and were sunk by gunfire or missile attack or disappeared of their own volition.

U-boats apportioned to the Allies under the Tripartite Naval Agreement, and Operations Cabal and Thankful, further reduced the number of surrendered boats available for destruction under Deadlight.

The entire question of the surrender and destruction of the U-boats remaining in May 1945 has been, unfortunately, the subject of much speculation, conjecture, supposition, misinformation and uninformed opinion by several authors since the end of the war. There were, for instance, no U-boat surrenders in Liverpool or Lisahally - those candidates had previously surrendered and been disarmed elsewhere. The only British ports to receive surrendering U-boats on active patrol were those two specified in the operational orders for Operation Pledge.