The Mrs Doubtfire star was due to return to the U.K. stage for the first time in 25 years in London theatre production We Are Most Amused on 12 November (08).

The show is part of the celebrations for British royal Prince Charles' 60th birthday.

But the comedian chose to warm up by playing an intimate gig to an audience of just 100 people at a student bar in the capital on Saturday (09Nov08) night.

The London School of Economics (LSE)'s regular comedy night The Chuckle Club played host to the superstar for the evening - but organiser Paul Jay was forbidden from revealing the identity of his surprise guest before the event.

Jay says, "It was the thrill of my life to have Robin Williams. He was marvellous - very, very funny."