The aim to raise what he calls, in classic whimsical Izzard style, “billions” for charity Sport Relief.

Just the one marathon race is enough for super fit modern athletes, and the pinnacle of achievement for “fun runners”. The suggested recovery time afterwards is two to three weeks.

And if he can run 43 marathons in a row, can it really be that difficult?The secret does not lie in strict training. Where athletes devote a life to running and amateurs clear the diary for months before a race, Izzard admits to only five weeks of prep.

Indeed, during the course of his schedule he has demonstrated what sports scientists call a “training effect” he has sped up instead of slowing down, from about 10 hours to just shy of five.

Before each race, his feet are bandaged. He has lost toenails, and one ankle ligament is seriously Nike LeBron 11 sore.

“My feet blistered up Air Jordan 23s terribly, then started healing when I shoved them in surgical spirit,” says Izzard. “Then they reblistered because you’ve got new skin coming through.

“Blisters upon blisters are not very nice. It’s the pain. Like the pain from mouth ulcers, it’s not a massive area but sharp and quite agonising.”

Daily ice baths are a necessary evil, he says, “to stop your legs inflating to twice the size of an elephant”.

Body eats itself

And internally there is more, albeit temporary damage, says sports scientist Professor John Brewer, of the University of Bedfordshire.

With each run sapping about 3,000 calories, Izzard’s body will be eating its own fat stores to keep going.

The force of four to five times his weight slamming through each foot, with every step he takes, takes its toll on muscles, tendons, ligaments.

Haemoglobin the blood protein which carries oxygen around the body will be broken down by the power of his own frame repeatedly crushing it in his feet.

So is completing these punishing runs Air Jordan 3 miraculous?

It seems not.

“He should be commended for showing that anyone can unlock that running potential,” says Prof Air Jordan 2s Brewer.

“Our bodies are designed to run because that’s genetically how we developed to catch food and avoid being someone else’s food. We have enough body fat to sustain about 40 marathons.”

Although it’s better to build up slowly, Izzard will benefit from reshaped muscles, more efficient organs, and boosted blood vessels.

And expert commentators are impressed by his endurance.

“In terms of the sliding scale of marathon runners, I would definitely put him closer to the Kenyans than to the man in the diver’s suit,” says Andy Dixon, editor of the racer’s bible Runner’s World.

“Covering 26 miles in a day at whatever speed for 43 runs, it’s demanding.

“A five hour marathon is a fairly decent pace. It’s a massive achievement. The big difference is raising yourself to do it again and again and again physically and mentally. I can only imagine the suffering he’s going through.”

The relentless runners in life, the real Forrest Gumps, do exist. Take American He man Dean Karnazes, a brawny type who brands himself Ultramarathon Man.

For him, 50 marathons across 50 US states in 50 consecutive Air Jordan 3 Retro days, only to run back to the start, is a mere jog.

Perhaps the real surprise is that the British equivalent is a once well upholstered comedian, and sometime wearer of heels.