Celebrity fundraisers: Just to watch is a feat of endurance

Whether swimming the Atlantic or running multiple marathons, they are raising the stakes

Ben Fogle yesterday preparing for his Atlantic crossing (PA)

Eddie Izzard may have failed in his bid to run 27 marathons in 27 days but the itinerant comedian has succeeded in fuelling a trend among celebrities that, to the slovenly and, perhaps, uncharitable observer, is as exhausting as any of the challenges they contrive.

Izzard had been raising funds for the Nelson Mandela Foundation by honouring the 27 years the former South African President spent in prison. But he was forced to postpone the challenge after four marathons due to reasons including "severe terrain, humidity and altitude".

The feat follows Izzard's 2009 challenge, in which he ran 1,100 miles around Britain for Sport Relief. It comes the day after Ben Fogle announced his plans to swim across the Atlantic for the homeless charity, Centrepoint.

The 1985 Live Aid concerts helped turn celebrities from endorsers into campaigners. The bar has risen higher still, forcing the famous to leap higher to prove their compassionate credentials. They swim, they cycle, they climb. What was wrong with gala dinners and dodgy charity singles? Is there a risk that we'll get too tired to keep up, even if they don't?

Mark Borkowski, the PR man, who counts Izzard among his former clients, sees extremes among such challengers. "There's a difference between the celebrity who does a marathon with no training and falls after the first 100 yards, and someone like Eddie," he says.

Anyone who followed Izzard's runs in 2009 will have struggled not to be awed – and it's hard to argue with the £1m he raised. But in the age of austerity (charities are facing cuts of up to £5.5bn this year), are challenges always the best way to raise funds?

A survey of young people by the research firm NfpSynergy last year found only one in five young people would support a charity because a celebrity endorsed it. Support decreased as respondents headed into their mid-20s. Charity Celebrity, an anonymous blogger and former consultant in the sector, says "converting awareness into cash" can be difficult for all but the most visible endeavours. She adds: "Charities need to think about the balance of this against the value of media coverage and income."

Ben Fogle is box office enough for Centrepoint and has guaranteed attention by aiming high. The presenter will become only the second person to swim the Atlantic if he completes the 3,000-mile journey to Cornwall from the US next year. But the charity admits it hesitated before signing on.

"Celebrity challenges are quite new to us," says John Ward, senior development officer at Centrepoint. "But when charities are struggling to raise funds, celebrities are a great way to raise awareness. We're confident Ben knows what he's doing." Let's just hope he finishes.