[Ernest_at_the_Beach]

Available at Amazon.

[colorado tanker]

Another good read:

[steelyourfaith]

Still have it in my library.

I believe that the public was not told the Enigma/Ultra story until about the time of the release of The Ultra Secret, the script on the book cover claims this was when it was first revealed.

A Man Called Intrepid was released a little later and has a section devoted to Enigma. Also fascinating.