By Jane Elliott
BBC News health reporter
Many people approaching the big 40 have a list of things they want to tick off - maybe sky-diving, visiting far-flung countries or trying a sport they have never done before.
A club foot hasn't stood in Mark Tointon's way
But as Mark Tointon, a keen sportsmen, approached his fifth decade he decided he wanted to run a marathon and signed up for New York.
Not previously a keen runner Mark, who was born with a club foot, suddenly found during training that he was enjoying it.
He decided to up the stakes and take on a "grand slam" of marathons - signing up for nine over a two year period.
And not just any old marathons. Mark's challenge is to complete the runs in all seven continents, and also taking in all the world's extremes in temperature and location - raising £50,000 for a children's hospital en route.
"As I was doing more running I became intrigued by doing a marathon in the extremes," Mark said.
"I knew about Ranulph Fiennes and the challenge he had taken on (running seven marathons on seven continents in seven days) so I decided to look at taking on this challenge of nine marathons in extreme conditions."
What makes his challenge all the more amazing is the fact that Mark, aged 40, from Broadstone, near Poole, in Dorset, has one leg three centimetres shorter than the other and one foot four sizes bigger than the other.
So he has dubbed his mission - the 7/11 Marathon Challenge - after his different shoe sizes.
Over a 16-year period as a child, Mark needed seven operations at Great Ormond Street Hospital to help rectify problems with his club foot.
He spent a total of two-and-a-half years in plaster.
He has decided to say "thank you" to the medics that helped him by donating the cash his running exploits will generate to the hospital.
The money has already been ear-marked to fund a newly equipped single room for a patient at the hospital - a project very close to his heart.
"I know how very important having some time out in a room by yourself can be when you are in hospital. I spent two to three weeks in hospital each time I went in.
"I wanted to get sponsorship and raise money and Great Ormond Street seemed the logical choice."
With the New York marathon already safely under his belt - completed in a time of four hours and seventeen minutes, the next date is January 2006 when Mark will fly to the Antarctic for the Antarctic Ice Marathon.
In April 2006 he will attempt the North Pole Marathon, before ticking off the European leg of his quest by completing the London marathon later that month.
In October 2006 he will brave wet jungle conditions in the Amazon marathon, and in February 2007 the Sahara Marathon will test his ability to keep going under a blazing sun and high temperatures.
Two months later he faces the Dead Sea marathon, and five months after that the Sydney Marathon in Australia. He will finish his epic in November 2007 by tackling the Everest Marathon.
Mark said: "Running nine marathons is quite a mammoth effort physically and people recommend taking a month off between each one, but I can't do that with all of them.
"I have the New York marathon under my belt now so I feel that I am on the way.
"I had set myself a four-and-a-half hour target and I did the run in an official time of 4.26. So that is inside my target."
Orthopaedic Surgeon Deborah Eastwood, of Great Ormond Street, said people like Mark were an inspiration to other youngsters with club feet.
"We will be enormously indebted to him for the money, but what I will be most indebted to him for is that he will prove that challenges like this are there to be taken.
"It is very reassuring from our point of view how well people can cope with these disabilities."
She said that the disparity in foot size and leg size would normally make the person more unbalanced physically, but that children with club foot, like Mark, often quickly learnt to compensate for this.