LITTLE Britain comedian David Walliams, right, is to take on the murky waters of the River Thames through Oxfordshire for his latest charity challenge.

Walliams — who raised more than £1m swimming the English Channel in July 2006 — will swim from Lechlade as far as the Houses of Parliament in London.

He will set off on his 140-mile, eight-day marathon, equivalent to seven lengths of The Channel, on Monday and is seeking sponsorship for Sport Relief.

He said: “Most people in the UK know the Thames, and most people think the idea of swimming in it is horrifying.

“And it is. It’ll be relentless.”

The funnyman said people should not to try and follow his lead, but instead donate to Sport Relief at sportrelief.com/ walliams.

Dates for when he will pass through Oxfordshire have not been announced.

Mr Walliams said he would burn the equivalent of 4,400 calories every day.

A documentary will be broadcast in the build up to Sport Relief in March 2012.