Some of the latest 'Our secret war' oral history interviews have been with women who, after joining the ATS or WAAF, were recruited into Y Service [wireless interception]. Following special Morse code training they were based at secret listening stations around the UK to monitor German radio transmissions which had been encoded using Enigma machines. Once intercepted the enemy's military messages, still in code, were sent to Bletchley Park - also known as Station X - to be decrypted by its talented, ingenious and, in many cases, eccentric code-breakers.
The secret military intelligence gathered in this way was code-named 'Ultra' and Winston Churchill called those involved his "geese that laid the golden eggs but never cackled" - in fact it's reported that in the early days of the war it was a FANY who was entrusted to personally deliver the decoded messages to him.
It was imperative that the Germans never realised the Allies had broken Enigma, and so very few people outside Bletchley Park knew that it was in fact the Government Code & Cypher School [GC&CS]. Everything was on a 'need to know' basis and the people stationed there knew little if anything at all of the other secret departments working right alongside them, let alone about those at the Y Service listening stations. They in turn had no idea of the significance of the messages they monitored nor where they were being sent, and everything connected with Enigma and Ultra remained a complete secret until long after the war when certain official records were eventually de-classified in the 1970s.
The work at Bletchley Park was later depicted dramatically in the Robert Harris novel 'Enigma' and its film adaption, but by comparison very little is known even now by the general public about the women and men of Y Service even though without them the BP decoders would have had nothing to work on.
The vigilance of the many hundreds of Y Service women and men at the listening stations around Britain and overseas ensured that it was possible to intercept the enemy's coded messages for decoding at Bletchley Park. In short, without the Y Service Bletchley would not have had the coded Enigma messages to decipher, and the work of these combined teams of many thousands of secret and silent heroes is now widely acknowledged as having shortened WW2 by at least two years.