Video: Paralympic champion Richard Whitehead prepares for marathon challenge

Paralympic gold medalist Richard Whitehead has said that he will take on his "biggest challenge" by running 40 marathons in 40 days this summer.

The London 2012 200m champion and world record holder will run a marathon a day from John O'Groats to Land's End for charity, starting in August.

Watch below for Whitehead's thoughts on the task ahead.