decoder keyboard

GCHQ and SIS: Putting the 'C' in codebreaking

The origins

During the First World War, both the Admiralty and the War Office ran successful code-breaking organisations. The Admiralty unit was called 'Room 40' (later 'ID25') whilst the War Office unit, after January 1916 was known as 'MI1b'.

A Government Code and Cypher School

Following a meeting of the Cabinet Secret Service Committee in 1919 and extensive negotiations, a single central organisation, the Government Code & Cypher School (GC&CS), was established to serve all government departments with signals intelligence and provide advice on the security of their own codes and ciphers.

Transfer to the Foreign Office

By 1921 it had become clear that there were no important foreign naval and military communications targets and that most of GC&CS's work was against diplomatic telegrams. So Foreign Secretary Lord Curzon asked that it be transferred to him. The Secret Intelligence Service (SIS) had followed a similar post-war trajectory determined by the same Cabinet Secret Service committee and the Foreign Office was confirmed as the Service's parent department. In September 1923 primary responsibilities for supervision of GC&CS were assumed by Hugh Sinclair, the second Chief of SIS.

SIS and GC&CS share a building

By 1926 SIS and GC&CS shared Broadway Buildings (54 Broadway, St James's), performing distinct activities and occupying different floors. In his GC&CS role, Sinclair took the title 'Director of GC&CS'. Although he was not involved in the day-to-day operations of code-breaking and construction, Sinclair or other senior SIS staff represented GC&CS over matters such as foreign relations and inter-departmental arrangements for radio and cable interception. Senior promotions, financial questions and internal organisation within GC&CS were approved by him.

Evacuation to Bletchley Park

In July 1938 Sinclair purchased Bletchley Park in Buckinghamshire as a wartime evacuation location for both his organisations. Both moved there in August 1939. Colonel Stewart Menzies, who succeeded Sinclair as C on the latter's death in November 1939, continued throughout the Second World War to lead GC&CS in its major organisational and inter-departmental development. Although GC&CS grew rapidly and was increasingly autonomous, Menzies retained strong personal control.

Restructuring GC&CS

At the turn of 1941/42 Menzies appointed a former Deputy Director of Military Intelligence to enquire into an Army-RAF conflict about decryption within Hut 3 at Bletchley which handled intelligence reporting from German army and air force 'Enigma' traffic. On the basis of the report, Menzies completely re-structured GC&CS, dividing it between civilian and Service work. The former, much smaller, part was moved away from Bletchley.

The much larger Service part remained at Bletchley. Early in 1944, under pressure from the Cabinet Secretary, Menzies expanded GC&CS's security resources. A new Deputy Director for communications security was appointed and Edward Travis, soon to be knighted, was upgraded to the title of Director while Menzies's title became Director-General.

SIS and GCHQ separate

In post-war planning in 1945 it was generally agreed that 'C' should continue to supervise both SIS and GC&CS which, from April 1946, formally took the title of Government Communications Headquarters (GCHQ). But this became increasingly difficult. During the war the requirements on the responsibilities of both GC&CS and SIS had expanded enormously while their work, analysis procedures and reporting lines had diverged. Many of GCHQ's activities such as large-scale radio interception, high-speed analytic machinery and massive communications networks had no pre-war parallels.

Menzies continued as Director-General until his retirement in 1952 and the title was retained by his successor, but when the latter retired in 1956 the title and GCHQ role for the Chief of SIS lapsed.