I have read several accounts of the sinking of the German minelaying submarine UC1 in July 1917. The majority of the accounts (J.M. Bruce, T.D. Hallam, Percy Clayton, Sturtivant and Page, Gordon Kinsey) state that it was sunk by an anti-submarine patrol of five flying boats from Felixstowe on 24 July. My grandfather, Flight Commander Arthur Cooper, was the pilot of the Felixstowe F.2c (N65) on that occasion and Lt. Commander John Porte was one of the crew. In these accounts three of the aircraft scored direct hits on UC1 with their bombs and oil, bubbles and wreckage were subsequently seen on the surface where the sub had gone down. My grandfather recorded the sinking in his log book and five years later he was given a prize bounty award of four pounds and sixteen shillings for his part in the action.
However, there are some conflicting accounts of the fate of UC1 which state that it was destroyed by mines off the Dutch coast five days earlier. This view is supported by Peter London in 'British Flying Boats', by J. David Perkins in his record of German submarine losses during WW1 and by the German website http://www.u-boot-net.de.
Does anyone know how and when this second version of events emerged? And if it was not UC1 that was destroyed on 24 July, which submarine was it? There must be records of a German submarine that was lost on that date but I have not found any.