New documents have been released about the birth of a secret intelligence pact between the US and UK 75 years ago.
The documents, including diary entries, detail the war time meetings that began at Bletchley Park and led to the UKUSA deal being signed in March 1946.
The alliance involved working together to intercept communications and break codes, sharing almost everything.
It grew into what is today called the “Five Eyes” pact of the UK, US, Australia, New Zealand and Canada.
“Together, we are greater than the sum of our parts,” said Jeremy Fleming, director of GCHQ, and director of the US National Security Agency, Gen Paul Nakasone, in a joint statement to mark the anniversary, amid talk of expanding the group even further.