Today we have made available to the public more than 100 previously top secret files from the Security Service, or MI5.

The records cover a range of subjects and span the First and Second World Wars and post-war era up to the late-1960s. Personal files include individuals classed as Second World War German intelligence agents and officers, Cold War-era Soviet intelligence officers, British Communists, and extreme right wing activists who came to the attention of MI5.

Many of the files related to the Portland Spy Ring case and the arrests and interviews of Gordon Lonsdale (KV 2/4429-4466), Ethel Gee (KV 2/4472-4474), Harry Houghton (KV 2/4476-4483), and Peter and Helen Kroger (KV 2/4484-4490).

Lonsdale, real name Konon Molody, was the illegal Soviet spy at the centre of the case, who received information from undercover spies Gee and Houghton who worked at the Admiralty’s Underwater Detection Establishment in Portland, Dorset. Lonsdale then passed the information to the Krogers, whose real names were Morris and Lorna Cohen, who then communicated the secrets obtained back to Moscow from their house in Ruislip. All were jailed for their roles in the spy ring.

Other highlights from the files which are searchable from KV 2/4409 to KV 2/4514 include:

Arnold Deutsch, the Soviet ‘illegal’ who took the lead role in recruiting the ‘Cambridge Five’ group of Soviet spies. The file includes a written confession by Kim Philby (KV 2/4428).

Politicians Konni Zilliacus (KV 2/4415-4417) and Manny Shinwell (KV 2/4425), who came to notice through their associations with the British Communist Party.

The French-born, wealthy American industrialist Charles Bedaux, who passed secrets to the Nazis during the Second World War (KV 2/4412).

There is also a selection of KV 6 files on the Cambridge Union’s first Communist president Pieter Keuneman, who later became a leading figure in the Communist Party of Sri Lanka (KV 6/147-151).

Professor Christopher Andrew, author of The Defence of the Realm: The Authorized History of MI5, has recorded a podcast giving a fascinating overview of the files in this release.