Stephen PullingerRunning 26.2 miles should hold no fear for former Norwich boxer Jackson Williams who three years ago managed to run 3,100 miles across the USA in just 111 days.Stephen Pullinger

Running 26.2 miles should hold no fear for former Norwich boxer Jackson Williams who three years ago managed to run 3,100 miles across the USA in just 111 days.

But ever one for a challenge, the 28-year-old Norwich City College sports teacher will be dodging 40,000 other pairs of feet - and running the whole way in the London Marathon barefoot.

Jackson, who prepared for his feat by last month running 100 miles from Norwich to London barefoot for Sport Relief, said: 'Running barefoot is not as comfortable as with shoes on so I'll be looking to finish in 3hr 30min to 4hr instead of a time of 2hr 40min I would normally expect to achieve.'

The race will incorporate an element of friendly rivalry as Jackson, whose main claim to fame in the professional ring was a losing bout to Olympic silver medallist Amir Khan, tries to beat fellow ex-boxer Jon Thaxton to the finish line.

Jackson is midway through a year of fund-raising events which he hopes will raise �10,000 for the United Nations Children's Fund.

And he is already looking ahead to fresh challenges - rowing across the Atlantic next year and a re-scheduled run across Australia in 2012.