The Little Britain star began his swim eight days ago at Lechdale in Gloucestershire and finished at Westminster Bridge.
The comedian’s efforts have so far raised nearly £1m for Sport Relief. Thousands of fans cheered him on as he reached the final stretch of his swim, one of the most gruelling parts of his journey as he battled the tides, debris and currents.
Supported by his wife Lara Stone alongside him on a boat, Mr Walliams was met along the way by fans and celebrity friends including comics Jimmy Carr, Miranda Hart and Rob Brydon.
The 40 year old said of the support he has received: “I never expected this to catch the public’s imagination like it has – there seems to have been a real carnival atmosphere around it which is lovely.”
Physical toll
Mr Walliams is a strong swimmer and has previously swum the 22 mile English Channel in a respectable ten-and-a-half hours, but his latest challenge has taken its physical toll.
He has suffered a bout of “Thames tummy,” brought about by some 500,000 cubic metres of sewage poured into the Thames in the past week.
It has left him with diarrhoea, vomiting and low energy levels.
But despite his health problems Mr Walliams managed to rescue a labrador dog over the weekend which was struggling to get out of the river near Cookham Lock in Berkshire.
The comedian’s mother, Kathleen, said: “I feel people think they’re part of this because they can actually see him doing it.
“He’s the, sort of, nation’s sweetheart because he’s doing this – rescuing dogs along the way and waving to people when all he wants to do is lay down almost. I’m very, very proud of him.”