Britain's spy agency has revealed the last messages from a German military communications network that were intercepted during World War II at Bletchley Park, the mansion house where Nazi codes were cracked.

The secret messages, sent on May 7, 1945, were made public for the first time on Friday to mark the 75th anniversary of the end of the war in Europe.

"British troops entered Cuxhaven at 1400 on 6 May -- from now on all radio traffic will cease -- wishing you all the best. Lt Kunkel," said the first recorded note.

"Closing down forever -- all the best -- goodbye," said the second that immediately followed.

They were sent as the Allies were closing in on Cuxhaven, a town on the northern coast of Germany, where the once-vast "German Brown" communications network had retreated to.

Britain's Government Communications Headquarters (GCHQ) released the messages, saying they showed how the Bletchley Park codebreakers had carried on working in the dying days of the conflict.

The codebreakers at Bletchley Park in central England are famous for having helped break the Germans' Enigma code during World War II -- as portrayed in the Oscar-winning 2014 film "The Imitation Game", starring Benedict Cumberbatch.