Walliams, 40, admitted three days after setting out from Lechlade, Gloucs, to swim to London's Big Ben: "I always knew there was a risk that taking in the water could cause problems. But now it's happened it has hit me really hard. I was sweating in the night and have been to the toilet a lot this morning."
The comic planned to complete the 140-mile charity swim in under eight days - but confessed the dose of "Thames tummy" had put him behind schedule
"This Thames tummy I've got is making the task seem incredibly difficult. London seems a long way away." As well as navigating a stomach-churning cocktail of bacteria he is also having to dodge river traffic.
As fans are continuing to turn out and cheer him on, Walliams was comforted at learning he has already raised more than £200,000 for Sport Relief.
The funnyman said of the cash that is flooding in: "It gave me a real boost."
By last night he had reached Wallingford Bridge, Oxfordshire, covering 14 miles in the day and 52 miles in total.
He was given a tearful hug from wife Lara Stone as he got out of the water.
The comic swam 17 miles on day one and 21 miles on day two.
News article written by Sarah Richardson
