David Walliams ends River Thames Sport Relief swim stage 'in pain' Published duration 5 September 2011

media caption Walliams sets off on Big Splash Thames Challenge for Sport Relief

Little Britain comedian David Walliams has finished the first stage of his swim along the River Thames in "a lot of pain".

Walliams stopped 2.3 miles (3.7km) short of his first scheduled stopping point shortly after 19:00 BST.

He started at the river's source near Lechlade, Gloucestershire, earlier and plans to finish at Big Ben next week.

The Sport Relief Twitter feed said Walliams had managed to swim 17 miles (27.3km).

The star had intended to swim to Northmoor Lock in Oxfordshire on the first day. To avoid disappointing fans who had gathered at the stopping point, he travelled by boat to greet them.

Hundreds of people cheered the star on as he began his challenge in the Gloucestershire town - where the water's temperature was 15C, currently colder than the English Channel.

'Masochist' swimmer

Earlier, Walliams said: "People often think of the Thames as just central London but there's 100 miles of it before you get to Teddington Lock."

"The great thing about the Thames is that people who live around it can hopefully come out and see me," he said.

Walliams added that when the swim got tough he would focus on "happy things".

"I think about songs and I have been on some trips with Comic Relief and Sport Relief and I think about the people the money raised will help.

"I must be a masochist. I wanted to do something else and I'd just turned 40 and I thought I haven't got much time left because my body is falling apart.

"I thought I better get on and do something because one day it's going to be too late."

He said the challenge, some 120 miles longer than his 2006 charity swim across the English Channel, would have its advantages.

"The nice thing about this, as opposed to the Channel, is the people can come out and see you. And seeing this part of the country."

During the swim, Walliams will battle powerful and unpredictable currents and undertows and will burn the equivalent of 4,400 calories every day.

He will also have to avoid the 39 million cubic metres of raw sewage that finds its way into the Thames every year after heavy rainfall - and swans.

"When I got here last night there were about 30 swans and I have been attacked by swans in the training, so I am actually quite nervous about them," the comedian said.