British actor Eddie Izzard has vowed to resume his charity marathon challenge next year (14) after "unforeseen medical complications" forced him to pull out of his 2012 attempt.

The comedian aimed to run 27 marathons in 27 consecutive days in honour of former South African president Nelson Mandela, taking in sites important to the anti-apartheid leader's history, including the area where Mandela grew up.

Izzard completed four races last May (12), but had to abandon his mission due to health concerns and tough running conditions.

However, the star has now revealed he is planning to sign up for a mega-marathon in 2014, and feels inspired to complete the challenge in honour of Mandela.

He tells Britain's The Sun, "I guarantee I will do it. I will drag myself round. I did think, 'What if I fail a second time?' But Mandela tried and failed, tried and failed. Then he had a bit of success and failed. I will do the same thing - I'll go again until I do it. Mandela is a big hero of mine."