Fiennes dashed from the pyramids to Cairo airport

Sir Ranulph Fiennes is one race away from completing seven marathons on seven continents in seven days, after finishing the sixth leg of the challenge on Saturday.

The British adventurer raced through the night in Cairo, after just four hours sleep following his completion of his London marathon on Friday in four hours 41 minutes.

He forged ahead through the heat and the busy Ramadan traffic, even managing to better his time of the previous day, says BBC correspondent Robert Hall.

The 59-year-old and his running mate Dr Michael Stroud, 49, then headed for a 6am flight to New York, where they hope to complete the marathon challenge.

Mike got really, really sick yesterday. He was urinating blood and had diarrhoea Sir Ranulph after Singapore What's happening to his body?

The pair have so far completed runs on the Falkland Islands, Santiago in Chile, Sydney, Singapore, London and Cairo.

Completed marathons

"Everything went off without any problems. He was in good health and ran the distance in less time than expected," Walid Ibrahim, one of the organisers, said in Egypt.

Fiennes flew from autumnal London to balmy Cairo after the fifth marathon

The Singapore leg, run in tropical heat and humidity, had been the biggest challenge.

Sir Ranulph described the experience as "hell on Earth", in which Dr Stroud walked much of the way after suffering a stomach upset.

Sir Ranulph said: "Mike got really, really sick. He was urinating blood and had diarrhoea."

Sir Ranulph has fought back from a heart attack and a double heart bypass operation to carry out his latest test of endurance.

He had already promised to take on the challenge before he collapsed on an aircraft in June and had to undergo surgery.

The pair have also been running with a defibrillator to safeguard Sir Ranulph's health.

All money raised from the Land Rover 7x7x7 Challenge will be given to the British Heart Foundation. They hope to raise a six-figure sum.