The FBI has been ordered by a judge in Los Angeles to release documents arising from MI5's surveillance of the singer-songwriter, John Lennon, in the 1970s.
The order is likely to lead to the release of further British intelligence papers which claim that Lennon donated funds to the IRA. The claim arises from a phone conversation monitored by MI5.
The order comes as a result of a 20-year campaign by an author and historian, Prof Jon Wiener. A professor at the University of California, Prof Wiener is the author of Gimme Some Truth, an investigative work on the FBI's files on the former Beatle.
It is believed that in the early 1970s MI5 gave details of its surveillance of Lennon to the FBI when the singer went to live in the US and campaign against the Vietnam war.
The FBI then set about finding a way to deport him, intensifying its surveillance of Lennon and his wife, Yoko Ono.
Prof Wiener applied for the release of the files shortly after Lennon was murdered in New York in 1980. He asserts that the documents to be released concern 10 other documents which are being withheld, presumably at Britain's request. The release of the first documents will make it difficult for either the US or British government to block the release of the other 10.
It is these documents that are causing most controversy. They are believed to detail how Lennon made donations to the IRA before the organisation's split into the Official and Provisional IRAs.
It is also understood that they detail similar contributions he made to the Trotskyist Workers' Revolutionary Party and to the Marxist magazine, Red Mole.
Speaking about the secrecy surrounding the files, Prof Wiener asserted recently: "We don't think the national security is really at stake here. We think this is 30-year-old, trivial information about the activities of a dead rock star."
Another document contains a report from a confidential source that Lennon donated $75,000 to a group planning to disrupt the 1972 Republican National Convention.
The American Civil Liberties Union, which backed Prof Wiener's attempt to obtain the files, said the FBI under the Nixon administration used surveillance in an attempt to deport Lennon because of his opposition to the Vietnam war.