Pink Floyd guitarist David Gilmour will take part in a sing-in protest against attempts to extradite UFO fanatic Gary McKinnon to face trial in the US over hacking the Pentagon.
McKinnon's mother Janis Sharp announced the news on microblogging website Twitter.
According to a report on The Register, Gilmour will not be at the protest, but will contribute to the backing track of a song.
The protest is planned to coincide with Barack Obama's visit to London for the G20 conference on the global economic crisis in April.
McKinnon is accused of committing the biggest military hack of all timeby hacking into 97 US federal and military computer systems, and of trying to get into 73,000 others where the US authorities say he causeddamage worth at least £350,000.
McKinnon was arrested in 2002, but the US asked for his extradition only in 2005. He has previously confessed to having entered US computer systems without authorisationin an attempt to find evidence of extra-terrestrial life and technology.