At this time of year, those brave souls planning to run the London Marathon are midway through their gruelling training schedules.

But one man from Wandsworth is preparing to run one of the world's most gruelling runs just four days before competing in the capital's most famous road race.

In March, Tom Fortune will run in the Marathon des Sables, a 144-mile (230 kilometres) race through the Sahara, to raise money for Trinity Hospice before heading back to the capital to compete in the London Marathon on April 13.

More than 600 competitors, from 25 countries, will take part in the 23rd Marathon des Sables, which is the equivalent of completing five-and-a-half consecutive marathons over six days.

Mr Fortune said: "Every day, as I run past Trinity Hospice, I think about the amazing work that is done there for those less fortunate than I am.

"Trinity was therefore the natural choice when I decided that I wanted to support a local charity - something that would make a difference on a local level - by my running efforts.

During the event, competitors will carry all their own kit in temperatures of up to 120F (49 centigrade) across uneven, rocky ground and sand dunes.

Mr Fortune, however, is no stranger to physical exercise as he has run all over the world, competing mainly in triathlons and shorter distance events.

Anne Hooper, chief executive of Trinity Hospice, said: "This is a truly amazing feat and we are so grateful to Tom for supporting the hospice in this way. We hope that others will, in turn, support Tom by visiting his JustGiving website."