Just some information that might be of interest,David Dowling did overfly USSR.From what he said all 4 RAF Pilots did at that time.As to Log books,he wrote to MoD before he died in 2008 to try and get something from them,unfortunately he didnt get any reply.His "normal" Logs exist with gaps when he was involved with the U2 and some other "weather reporting",(51 Squadron I think),in the early '60's.