PEDAL power is what one ambitious cyclist hopes will carry him on three wheels the length of Great Britain.

Determined Andrew McKenna hopes to claim an unofficial cycling record when he sets off on the 840-mile route from Land's End to John O'Groats tomorrow.

The 46-year-old writer and journalist of Cheriton has already clocked up more than 3,000 miles in training on his American-made Catrike Human Powered Vehicle - also known as a recumbent sports trike.

Now, he is set to cycle about 120 miles a day, from gruelling climbs across Bodmin Moor, up the Lake District's notoriously steep Shap Fell, and through the Scottish Highlands.

"I'm not worried about the human powered vehicle," he said. "It's far more comfortable than any bike - no aching arms, neck or backside. It's like a travelling deckchair.

"It's fast too, astonishingly so downhill."

Andrew, who is married to Carol, hopes thinking of the two good causes he is raising money for through his sponsored Great Trike Trek will help him succeed.

As he reaches downhill speeds of up to 45mph he will be raising funds for the Friends of Cheriton School, where his nine-year-old son Hugo is a pupil, and the Midhurst-based charity Canine Partners.

"My main concern is me. After putting in all the training - and putting up with all the attention - I'd hate to do something daft, like pull a muscle and wimp out.

"But I'm determined not to disappoint my two good causes - or all those people who've waved and honked."

The adventurer will be helped on his way by friends Christine O'Leary, of Bishop's Waltham, and Ben Harvey, of Swanmore, who will track him up the country in a luxury motorhome courtesy of Marquis Motorhomes' showroom at Lower Upham.

Andrew's own cycling equipment is being provided by Hargroves Cycles.