Dear James,

Can I suggest that you take a look at the excellent bibliography at the end of Clay Blair's Vol. 2 (Hitler's U-Boat War - The Hunted 1942-1945).

There are several references to both U-40 and U-42, as well as links to the appropriate files at NARA Washington and TNA Kew.

So, perhaps a visit to one or the other, or getting a researcher to take a look for you, might produce the results that you are after.

Hope this helps (but sorry if you have been there already).

Yours aye,

Derek.