Re U577 - David Balme did a winter lecture at the Yacht Club one Wednesday evening, and with permission showed a clip from U577, then the bit added at his request, making clear the film was a work of fiction, based on the exploits of Sub Lt Balme and HMS Bulldog. I was at Bletchley Pk a few days back and mentioned David, and all the staff knew of him, but even more enthusiastic about Maj Hugh Skillen, Historian of BP, and many years ago my French master.