"The papers are thought to be of particular historical value as much of Turing's war-time work was destroyed under the Official Secrets Act and the man himself kept few personal possessions."
Yes - thats the point, all the interesting stuff - the notes on enigma and the invention of the computer are gone.
All we have are a bunch of preprints from the 30s - but these are preprints of journals that do exist
(note to those under 50 : upto to the 1980s journals would send you a few dozen unbound copies of your paper for you to distribute - before photocopiers were common)