This is the epic story of what happens when nine celebrities attempt the ultimate endurance challenge for Comic Relief - a gruelling 100km trek across a desert in Northern Kenya. Fighting exhaustion, blisters, scorpions, stomach bugs and temperatures pushing 50 degrees Celsius, it is an adventure they will never forget. Dermot O'Leary, Ronni Ancona, Craig David, Lorraine Kelly, Scott Mills, Olly Murs, Nadia Sawalha, Kara Tointon and Peter White meet people who are losing their sight, and spread the word about an eye care camp where they can receive treatment. Keeping with Red Nose happenings; there's a highlights show from David Walliams' day-long panel show marathon, 24 Hour Panel People, at 10.30pm on BBC3. Among the guests are Jack Dee, Stephen Fry, Miranda Hart, Jason Manford, David Mitchell, Dara O Briain, Paul O'Grady, Sue Perkins, Jo Brand, Jimmy Carr, Lee Mack, Charlie Brooker and...... Jed