David Walliams has said he will press on with his Thames swim despite the news that half a million cubic metres of sewage has found its way into the river.

The waste has been flowing into the Thames after being diverted by Thames water, following a bout of heavy rainfall in London which threatened to block up the city’s Victorian sewers.

However Walliams has said he is undeterred – despite already having fallen victim to a bout of ‘Thames tummy’ as he undertakes the eight-day swim for Sport Relief.

“We’ve been in touch with David Walliams’ team and he’ll have to make his own decisions,” said Richard Aylward from Thames Water.

“We’re not public health experts but I wouldn’t recommend swimming in it. That said, David is doing a hugely admirable thing and we wish him all the best.”

Walliams has passed the 100-mile mark of his swim, which began in Gloucestershire and will take him up to London landmark Big Ben – and has so far raised over £500,000 for the charity.

And he was hailed a hero on Saturday after he rescued a Labrador called Vinny – who was struggling to get out of the water due to having a bad hip.

“I heard a splash and looked over to be met with the face of a sweet Labrador,” David said. “I thought he was fine, but he started to really struggle when he was getting out so I swam over and helped his owner get him out.”

The animal’s owner Steve Outten, 23, from High Wycombe, added: “Vinny has hip dysplasia and was really struggling to get out just as David was swimming past. He stopped, swam over and helped me get him out, which when you think what he’s going through with the swim is totally amazing, what a man.”