Late-night sherry was key to forging special relationship

GCHQ files never seen before show how Britain’s “special relationship” with the US was built over “a midnight glass of sherry”.

New details from the private diary of the first head of GCHQ reveal how the intelligence relationship between the UK and US evolved during the Second World War.

In a diary entry Commander Alastair Denniston, then head of GCHQ’S predecessor the Government Code & Cypher School, noted: “The Ys are coming!” (Y being shorthand for Yanks) referring to a meeting with US cryptologists. On Feb 10 1941, he noted: “Y’s arrive.”

Commander Denniston told Barbara Abernethy, his assistant, of the visit from the US Signals Intelligence Service: “There are going to be four Americans who are coming to see me at 12 o’clock tonight.

“I require you to come in with the sherry. You are not to tell anybody who they are or what they will be doing.”

The relationship flourished during the visit and intelligence was shared, including Britain’s greatest secret – the Bombe machine, designed by Alan Turing and Gordon Welchman to break the German Enigma cipher.

The visit to Bletchley marked the start of the so-called special relation- ship. With the inclusion of Canada (1949) and Australia and New Zealand (1956) the modern-day 5-Eyes alliance was established.

Jeremy Fleming, the GCHQ director, and General Paul Nakasone, the head of the US National Security Agency, said: “This year, we celebrate the 75th anniversary of the formal partnership between the UK GCHQ and the US National Security Agency.

“This alliance defines how we share communication, translation, analysis, and code breaking information, and has helped protect our countries and allies for decades.

“The modern digital world is constantly evolving. Threats don’t respect international borders. Global partnerships are key to our security and economic prosperity – and none more so than the one between our two countries.”

They said the alliance grew stronger with the addition of Canada, New Zealand and Australia. “Together, we are greater than the sum of our parts.”

The first formal signals intelligence agreement between the UK and US (originally called BRUSA), was signed in Washington on March 5 1946, the same day as Churchill’s Iron Curtain speech.

It was not revealed until 2010, when the document was released to the National Archives.