This gruelling six-week challenge will take place next March along the London Marathon course - but how it will it work, and how did it come about?

Whose crazy idea was this?

On Wednesday 12 July 1809, noted sportsman and infamous gambler Captain Robert Barclay was challenged to undertake a unique feat: running one mile every hour for 1,000 consecutive hours.

That meant covering a mile every hour for nearly 42 consecutive days.

THE ORIGINAL NUTTER Name: Captain Robert Barclay Allardice Born: 1779 Attempted: 1,000 miles in 1,000 hours At: Newmarket Heath Won: 16,000 guineas

Barclay chose Newmarket Heath as the venue for his escapade.

With the help of supporters who slapped him round the face to keep him awake, and a pair of pistols to combat the gangs who attempted to nobble him, he somehow pulled it off.

How? Mainly by running two miles at a time - one mile at the end of one hour and one mile at the start of the next.

This allowed him the maximum rest period of anything up to an hour and 45 minutes, depending on how fast he ran.

Barclay lost 32 lbs (15 kg) in weight, but recovered quickly enough to sail off to the Napoleonic Wars just eight days later.

His prize for completing the astonishing feat was 16,000 guineas - the equivalent of 320 years' worth of wages for an ordinary working man.

Once was enough, surely...

You might think so, but Flora, sponsors of the London Marathon, have decided to replicate Captain Barclay's amazing feat.

The event will start at 1600 GMT on Sunday 2 March 2003 in front of Buckingham Palace.

One thousand hours later, sometime after 0800 GMT on Sunday 13 April, the challenge will finish on Blackheath Common.

By that stage, the competitors will have run or walked up and back along the course of the London Marathon more than 38 times.

But the endurance test does not end there. Competitors will complete the challenge just in time for the start of 2003 Flora London Marathon - which they then have to run.

How tough will it be?

The challenge facing the competitors is enormous.

ALTERNATIVE DESTINATIONS London to Leeds: 170 miles To Paris: 213 miles Milan: 596 miles Madrid: 783 miles Lisbon: 985 miles

Participants' ability to handle interrupted sleep is just as important as physical running ability.

In order to enjoy the maximum amount of rest possible, competitors will target 15-minute miles.

The aim then will be to run two miles at a time - one mile at the end of the hour and one mile at the start of the next.

This means competitors will potentially have 90 uninterrupted minutes in which to sleep.

The challengers

More than 170 people applied to compete in the 1,000 Mile Challenge.

After regional trials in Brighton, Bristol, Birmingham, Manchester and Glasgow, 43 candidates emerged.

At each trial each had to run a mile an hour for 24 hours, as well as undergoing rigorous physical and psychological screening.

The top 11 candidates from the regional heats were then invited to interviews in London and the final six challengers selected from there.

The names of the lucky six are announced on Tuesday.