Turing's (still?) classified inference engine algorithm?
This doesn't answer your question, but you may find clues in two wartime papers of Alan Turing which were formerly classified were declassified and published in the UK National Archives in 2015, and are now available on the arXiv:


  Alan M. Turing, ‘The Applications of Probability to Cryptography’, UK National Archives HW 25/37, 1942, arXiv:1505.04714.
  
  Alan M. Turing, ‘Paper on Statistics of Repetitions’, UK National Archives HW 25/38, 1942, arXiv:1505.04715.


It may be possible to reconstruct, from the principles enumerated therein, what algorithm Turing would have implemented in the Colossus to perform the feats it is known to have been able to perform.