sentences:  The British cryptologist Harry Hinsley, then working at Bletchley Park, realised at the end of April 1941 that the German weather ships, usually isolated and unprotected trawlers, were using the same Enigma code books as were being used on U-boats.The trawlers, which transmitted weather reports to the Germans, were being sent naval Enigma messages.Although the weather ships did not transmit enciphered weather reports on Enigma machines, they needed one to decode the Enigma signals transmitted to them.