You'll know him better as one half of the Little Britain comedy duo, but he's also been making a name for himself in recent years as a bit of a super-athlete.
Five years ago, David Walliams swam 21 miles across the English Channel, raising £1 million for the
Sport Relief charity in the process.
Then three years ago he swam the Strait of Gibraltar between Spain and Morocco, again for Sport Relief.
And last year he swapped the swimming trunks for cycling shorts and biked it from John O'Groats to Land's End.
But his latest adventure will be his toughest - Walliams is hoping to
swim 140 miles along the River Thames from Lechlade in Gloucestershire to Big Ben in central London. The swim is scheduled to begin on 5th September and finish eight days later. Yes, that really is
eight days of swimming, covering a distance of
140 miles.
The epic swim - again for Sport Relief, as part of the
Big Splash campaign to get the nation swimming - will involve Walliams spending up to eight hours a day in the Thames battling strong currents and dodging oncoming boats as he works his way towards Big Ben.
And while the quality of the water in the Thames is far from being the health hazard it once was, it's still something you don't want to ingest.
So it's not only a very tough swim for the funnyman, it's also rather dangerous. I certainly don't think there's going to be much laughing involved.
No doubt Walliams would love nothing more than to see members of the public along the route, offering shouts of encouragement from the riverbank and bridges.
He'll be passing through many English towns along the way, including Oxford, Reading, Henley, Maidenhead, Windsor, Kingston and Richmond. Or you could simply clap him in to the finishing line when he turns up at Westminster Bridge (hopefully) eight days after setting off. Keep in mind, eight days is just an estimate.
On top of that, you could also
sponsor his epic feat. Money donated to Sport Relief will help to improve the lives of people in the UK and all over the world. Click here to find out how to donate.
