RAF Topcliffe Mainbrace Disc: a silver disc trails a Meteor jet over North Yorkshire

September 1952. NATO was in the middle of Exercise Mainbrace, a 13-day exercise that simulated a Soviet attack on Western Europe. At RAF Topcliffe, near Thirsk in North Yorkshire, Shackleton crews of 269 Squadron, Coastal Command, were on the airfield. Ground crew were refuelling two Shackletons.

Friday 19 September. 10:53 am. A Meteor jet was descending towards nearby RAF Dishforth. R.N. Paris spotted something behind it. A white object, about five miles astern. Flt Lt John Kilburn described it as "silver in colour and circular in shape," at an estimated 10,000 to 20,000 ft. The crews first took it for "a parachute or cowling from a meteor."

It did not behave like either. It held a slow forward speed, then began to descend, "swinging in a pendular motion…similar to a falling sycamore leaf." When the Meteor turned towards Dishforth, the object "appeared to follow." Then the swinging stopped. It "began a rotary motion about its own axis."

Then it "suddenly accelerated at incredible speed in a westerly direction," turned onto a south-easterly course, and was gone. The whole manoeuvre lasted 15 to 20 seconds.

"The acceleration was in excess of that of a shooting star," Kilburn wrote. "I have never seen such a phenomenon before." He told the Sunday Dispatch it was "something different from anything I have ever seen in 3,700 hours flying in a variety of conditions."

Accounts give about ten witnesses, among them Flt Lt M. Cybulski and Master Signaller A.E. Thompson. The squadron's Operations Record Book called them "reliable." The story ran in the Yorkshire Evening Press the next day, then in France-Soir and the Australian press. An RAF spokesman would only say: "It is being investigated." At Topcliffe the squadron joked about a new badge, an "airborne NAAFI saucer" under the motto "Omnia Videmus."

The report went through MHQ Pitreavie and HQ Coastal Command to the Air Ministry, with copies for the Director of Scientific Intelligence. Ralph Noyes, then Private Secretary to the Vice Chief of the Air Staff, saw the signal. Years later he called it "a minor and not particularly dramatic sighting of what came to be known to ufologists as a 'daylight disc'." He remembered "embarrassed unease" that "our own people" were taking saucers seriously.

In December 1952 a CIA memo by H. Marshall Chadwell mentioned the "Yorkshire incident." It said R.V. Jones's committee was still investigating, and that Jones was "distressed" by the publicity. No formal finding survives. A 1967 memo by John Dickison of DI55 found no evidence the object came from the Meteor. Its trajectory was never established.

A ministry spokesman said the "object could have been a meteorological balloon." An RAF officer suggested a smoke ring from a jet engine that cut out and relit, catching the sun. The RAF said no cowling or parachute had fallen near the station. A Sunday Dispatch subhead gave the crews' answer: "NOT Smoke-Ring Or Weather Balloon, Says Pilot." David Clarke suggests that personnel on high alert during the exercise would notice things they might otherwise ignore.

Edward J. Ruppelt later wrote that the Mainbrace sightings "caused the RAF to officially recognise the UFO." Clarke, who found the files at The National Archives while writing Out of the Shadows with Andy Roberts, traces the Air Ministry's UFO desk back to Topcliffe. It ran for 57 years. It closed in 2009.