The United Kingdom Government started investigating unidentified flying objects beginning in 1947. According to press accounts the Royal Air Force accumulated a large number of reports. Unlike the Project Blue Book files, the corpus of these UK government investigations between 1947 and the early 1960s allegedly was destroyed as a matter of official policy. We cannot check the validity of rumors from the Hong Kong press of British fighter aircraft pursuing UFOs over the colony in July 1947, nor can we check an American reference to radar trackings by a British warship near Japan in 1948. However, as with US government records, various UK UFO items are found in other files and dossiers. Operation Charlie, a January 1947 radar incident was one such incident.
Operation Charlie January 1947 Radar Case by David Clarke with Analysis of Radar Trackings by Martin Shough:
Another important UK document, The Flying Saucer Working Party was found after a mention in Gerald Haines' CIA article CIA's Role in the Study of UFOs, 1947-90 - A Die-Hard Issue.
Press and other unofficial sources, just as in other countries, carried numerous unofficial reports and sometime official and military reports which made it into the public domain. Reports from US forces in Great Britain and even a few pieces of UK government information can be found in Project Blue Book and other US government files. Some reports even raised questions in the Houses of Parliament. Such exposure in the 1960s put an end to the automatic destruction of UFO records; however, most official files remained unavailable to the public.
See Julian Hennessey: The UK Government and UFOs:
Questions in the House of Lords provided a list of UFO records held by the government. Later, declassification and release of large collections of UFO records took place. In addition requests under the recently passed Freedom of Information Act and research in various official archives have revealed more records, some even from the period when most records were routinely destroyed.
Newly Released UFO Files from the UK Government:
Ministry of Defence Freedom of Information website: (use UFO search term)
Dr. David Clarke's Blog
Major Donald E. Keyhoe, first as an individual and later as Director of NICAP, did try to contact foreign governments for UFO information including British officials. Most inquiries prior to Julian Hennessey's efforts were politely turned aside. One letter which elicited a positive response is linked below.
Teletype referencing one of the UFO cases mentioned in Major Keyhoe's letter:
At CUFOS a small number (about a half dozen) official documents were found among Dr. Hynek's papers, all dating from the early 1950s. One is a “Restricted” signal sent to UK Headquarters Coastal Command regarding a UFO sighting at RAF Topcliffe during a major NATO exercise. The other two are letters detailing two separate UFO incidents. One is a sighting by base personnel at Royal Air Force Station Winthorpe, and the other a letter from a British schoolboy reporting an extended UFO observation. The markings on the letter are Hynek's evaluation codes.
Restricted Topcliffe Teletype:
(Detailed overview of the "Topcliffe Incident" by Dr David Clarke)
Restricted report from Royal Air Force Police MPs at RAF Winthorpe
Letter from a British schoolboy reporting an extended UFO observation (Note: Markings are Hynek evaluation codes)
We do not know how Hynek obtained these reports. Were they the result of an early visit to the British Air Ministry during which the records were given to Hynek? Were they released to Hynek by a visiting British official, or were they passed along to him via Project Blue Book?
— Jan L. Aldrich