Eddie Izzard's charity marathon challenge in honour of Nelson Mandela in May (12) was brought to a halt when the comic suffered an adverse reaction to a prescription drug.

The Brit set out to complete 27 marathons in 27 consecutive days in South Africa to represent each of the years the country's former president spent in jail, but after completing four, he had to pull out.

Izzard blamed "unforeseen medical complications" at the time, and now reveals he was forced to retrain for the event due to the effect a prescription pill was having on his body.

He tells BBC News, "I started doing 27 marathons in 27 days in honour of Nelsen Mandela, I did four. I got a problem with my body because I was taking a certain prescription drug and I had to stop and retrain. I will go back, I promise. I will return and do the whole thing. I won't give up."