consistently for much of the rest of the war. As a reencodement it was easy and if Sucker or Dolphin had a triplet so that they were "out of step" the 2 keys could be cross ruffed almost ad infinitum.
On November 1st Dolphin, Plaice, and Trumpeter changed to the 4 wheel machine and we were left without a major key on 3 wheels. This long expected development came too late to cause us any serious difficulties and simply meant that in future all jobs required 4 wheel bombes. A more serious aspect of the matter was the difficulty which we foresaw would arise if the bigram tables were to change. The methods used for building up bigram tables in the past had involved breaking messages in ways which were not possible on a 4 wheel key and it was necessary to invent some other way of breaking large numbers of messages. The problem of creating a machine which would run at high speed large numbers of cribs on individual messages was put to Squadron Leader Jones who evolved the Fillibuster. In March we were to have cause to be thankful for the existence of this machine although it was not used for the purpose for which it was originally intended.
December brought 2 new developments on Shark and one new key. At the end of the month a message on Dolphin reminding operators to change their reflector combination was widely misinterpreted as implying that the reflector combination would change more than once a month in future: this scare caused more of a sensation in Naval Section than amongst ourselves who had now become sceptical about messages which might be interpreted as heralding some unlikely development.