A man from Hertfordshire has embarked on a challenge to run 100 marathons in 100 days.
Matthew Loddy, from Berkhamsted, began in southern Portugal on Saturday.
He plans to run along the Algarve coast into Spain, over the Pyrenees into France and through the channel tunnel before competing in the London Marathon on 22 April.
The fitness enthusiast hopes to raise £100,000 for the Framework Foundation charity.
"It's going to be very tough, but hopefully with all the training I've done it will be possible," he said.
"It's injuries that will be the biggest problem and cause the greatest risk of not completing the run," he said.
Mr Loddy explained how the challenge was inspired by a promise to his friend Phil Latham, who died from stomach cancer, aged 36.
"We had agreed to do a sponsored walk from London to Portugal together.
"Unfortunately, just after Christmas 2010, Phil was diagnosed as only having a few weeks to live. I jokingly said 'you're letting me down, I'll have to do it on my own'."
Mr Loddy hopes to complete each marathon in a maximum of five hours, but says he is prepared to run for up to eight hours a day if necessary.
"As long as I do the right things I can get through it," he said.