Documentary looking back on the eight day swim that comedian David Walliams undertook for Sport Relief 2012.

Providing the inside story and exclusive behind the scenes access, the documentary takes in all the highs and lows of the outstanding challenge that saw David pass through seven counties, make 111,352 strokes, burn 68,000 calories, battle a serious bacterial infection and even save a dog from drowning as well as enjoy visits from fellow comedians Miranda Hart, Rob Brydon and Jimmy Carr.

Sports personalities Michael Vaughan, Ben Cohen, Gabby Logan, Tyson Fury and Neil Ruddock face their toughest challenge to date - performing a stand-up comedy set to a packed audience. Each is paired with a top stand-up in Patrick Kielty, Jason Manford, Andi Osho, Chris Ramsy and Dan Sloss, but with less than two weeks to get a set together, it is not just the sports stars who have a challenge on their hands.

On 22 January 2012, Blue Peter's Helen Skelton completed an epic 500-mile trek to the South Pole for Sport Relief, using three modes of transport: kite skiing, cross country skis, and - in a world first - by bike. This is the story of how she made that gruelling journey, experiencing temperatures twice below that of a household fridge freezer. As well as dealing with temperatures of -36 degrees, she had to battle with blisters, not washing for weeks on end, and a cough that threatened to give her pneumonia.

John Bishop takes the word 'triathlon' to new heights in an extraordinary physical and mental challenge for Sport Relief. John cycles, rows and runs from Paris to London, accompanied by celebrity supporters like Davina McCall, Chris Moyles, Freddie Flintoff, Dermot O'Leary and Frank Skinner.

This incredible challenge pushes John to his limits, and the only way he keeps going is remembering why he is doing it in the first place - to raise money for Sport Relief. John visits Sierra Leone to see the incredible work done by Sport Relief, and learns how vaccines that we all take for granted in the UK can save lives.

This intimate and honest documentary captures the laughter and the tears as John battles with intense pain and exhaustion in his determination to succeed.

The Sport Relief marathon continues on BBC2 with David Walliams and Miranda Hart taking over the presenting duties. Sporting royalty Zara Phillips and Sir Steve Redgrave join the cast of Twenty Twelve as the spoof organisers of the 'Olympics' produce yet another fine mess en route to the Games, while Jake Humphrey presents a special Never Mind the Buzzcocks with Louise Redknapp and Mel C alongside the regulars.

John Bishop, Fearne Cotton and James Corden are in the hot seat as Kate Moss, Stella McCartney, Colin Jackson and Linford Christie are among the star names appearing with Jennifer Saunders and Joanna Lumley in a special edition of Absolutely Fabulous for Sport Relief. There's also a special edition of Question of Sport, with 'Sue Barker' as you have never seen her before!