David Walliams swims through Teddington for Sport Relief

David Walliams got into the River Thames at lunchtime today as he starts another deep water challenge for Sport Relief.  Starting up in Gloucestershire, if all goes according to the swim plan, David will reach us here in Teddington on Saturday, 10th September.

This is a huge swim challenge, it's 140 miles in total and the swim will finish at Big Ben next Tuesday. The freezing cold river water can result in cramp and breathing spasms known as a 'gasp reflex'. There'll be strong currents and he will burn approximately 4,400 calories every day. He'll need to avoid the traffic on the river and deal with bacteria such as e-coli, salmonella and hepatitis - and 39 million cubic metres of raw sewage that finds its way into the Thames every year after heavy rain.

David said: "Most people in the UK know the Thames, and most people think the idea of swimming in it is horrifying!  And it is.  It'll be relentless. It's a huge distance so I'll need all the support I can get.  It's really not a safe environment to swim in – people really mustn't try this, I have an incredible team of experts to help keep me safe.  If there's a lot of rainfall there'll be a lot of sewage present so I've had to have loads of jabs.  And aside from anything else, you can't see anything! There's zero visibility in the water - I won't even be able to see the end of my arm."

This is the latest idea from David himself and he's been training for the swim for many months.  You may remember his cross Channel swim and then him swimming across the Strait of Gibraltar too.  Last year, David did the cycle trip from John O'Groats to Land's End.

He's looking for sponsors at Sport Relief.  And he's hoping that people will cheer him on throughout the race too.  You can check out the GPS tracker online and follow the Twitter feed using #thamesswim to see where he'll be. 

We'll let you know the time David should reach Teddington next weekend and hope you'll join us at Teddington Lock to cheer him on!

Images by kind permission of Sports Relief