Fearne Cotton off to a bumpy start as stars get on their bikes for Sport Relief

She successfully scaled Mount Kilimanjaro last year, but Fearne Cotton has been having a little more trouble conquering the streets of Buckinghamshire.

The TV presenter – who joined celebrities including Cheryl Cole and Gary Barlow to climb Africa's highest peak for Comic Relief in 2009 – is currently preparing to cycle across the country in aid of Sport Relief.

Headed up by recently-engaged David Walliams, a team of British stars - comprising of Fearne, Davina McCall, Jimmy Carr, Miranda Hart, Russell Howard and Patrick Kielty – will attempt to ride their bikes 1,000 miles nonstop from John O'Groats to Lands End beginning on March 1.

And ahead of the challenge, the 28-year-old has been putting in some practice – picking up a few bumps and bruises along the way.

Writing on her blog, Fearne told her fans: "At the weekend myself and David Walliams…headed out of Marlow where our wonderful trainer Greg lives. He took us on a 90 minute cycle of doom around the local hills."

"I unintentionally dismounted (fell off) twice, and David got four punctures in 90 minutes which I believe is a world record," she said.

"We look the part in our shiny red jackets and fancy cycling shoes, but are generally terrible at cycling. I'm more than nervous about this challenge looming."

Unfortunately for the Radio 1 DJ, one of her 'dismounts' has been made available for all to see thanks to a video released by Sport Relief. It shows her cycling behind the Little Britain star before their wheels touch, causing her to fall off her bike into a parked van.

While some of the participating famous faces are struggling, David and Davina are said to be performing well.

Both have illustrated their physical fitness in the past – Big Brother host Davina has a range of successful fitness DVDs, while the 38-year-old comedian swam the Channel for Sport Relief in 2006.