Norton foregoes the usual physical challenges beloved of Comic Relief for a more sedentary affair: attempting to set the Guinness world record for most questions asked on a TV chat show, which should see him broadcasting into the wee hours of Friday morning. We can only hope that Graham also dispenses with his usual tipple of wine with guests, otherwise this chatathon is going to get very messy.

So far guests announced as appearing on the sofa include Ronnie Corbett, RT's Sarah Millican, Martin Freeman, Elle Macpherson, James Nesbitt, Louis Smith, Heston Blumenthal, Warwick Davis, Russell Tovey and Jimmy Carr, though you wouldn't bet against an American superstar or two turning up, too. Music acts will include Example, Paloma Faith, Hurts and Laura Mvula.

Graham will be assisted by co-hosts Terry Wogan, Frank Skinner and Nick Grimshaw, and viewers can help, too, by submitting questions via Twitter and Facebook. And by donating money.

Russell Howard mocks Nick Grimshaw

The comic has had a pop at Radio 1 Breakfast Show host Nick Grimshaw for hanging out with younger famous pals like Harry Style.

Unique behind the scenes access to the BBC Fringe

Over 24 days of the Edinburgh Festival Fringe the BBC venue will be jam-packed with familiar faces from BBC TV, radio and online. Nick Grimshaw, Nina Conti, Paul Merton and Nicholas Parsons are just some of the names appearing live at the venue, not only recording shows on site but also taking people behind the scenes to explain how BBC shows are made.