While the average park jogger covers no more than ten miles in a week, super-fit Brian Kirkdale is raising the bar by running eight marathons in eight days.
Mr Kirkdale, of Burgess Hill, is one of 16 athletes taking part in the gruelling 230-mile Paris to London race, which starts on Sunday.
The final day of this mammoth endurance test will take in the London Marathon.
The 46-year-old test engineer said: "It's more than a race - it's a challenge to get to the finish in one piece."
Mr Kirkdale, who has been running for 30 years and is a member of Hastings Runners, is used to extreme feats of fitness.
He has run up and down Ben Nevis every year since the late Seventies.
And he has competed in the Comrades Marathon in South Africa - a 56-mile race with a 12-hour deadline for finishers.
He said: "It's really quite an event with in excess of 12,000 runners. I've done it ten times and always finished in 12 hours."
His fastest time so far has been seven hours and 48 minutes in temperatures exceeding 27C (80F).
But Mr Kirkdale believes his latest challenge will break new ground. He said: "I've never done a multi-day event before.
"I've done training where I run a couple of marathons back-to-back but to get up every day and be running for about four to five hours, I've no idea how it's going to feel."
Mr Kirkdale said the key to success is avoiding injury and not pushing himself too hard in the early stages. He added: "It's all about making sure you get through each marathon so you can run the next day."
He has been training for the big event by running for ten hours a week and recently completed the Bungay Marathon in Suffolk, finishing in 3hr 39 min.
The Paris to London challenge will include stages taking in Newhaven to Telscombe Cliffs.
Mr Kirkdale is hoping to raise about £2,000 for two charities, both of which help vulnerable children overseas. Sponsor him at kirkdale.members.beeb.net
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