text: Explorer Sir Ranulph Fiennes has become the oldest Briton to complete the punishing Marathon des Sables with just 13 minutes to spare. At the finish line of the six-day 256km race through the Moroccan desert, the 71-year-old, who has previously suffered two heart attacks and underwent a double heart bypass in 2003, said the event is 'not set for old geriatrics like me'. There were fears Sir Ranulph would not be able to finish the event after the 91km fourth stage, when he ran for more than 30 hours in temperatures topping 50C having had just one hour of sleep. Scroll down for video . Victory: Sir Ranulph Fiennes has become the oldest Briton to complete the Marathon des Sables in the desert . The veteran explorer has previously suffered two heart attacks and underwent a double heart bypass in 2003 . Speaking after completing the race, the veteran explorer, who has raised almost £1million for Marie Curie, said: 'The main thing is this race is not set for old geriatrics like me. 'When you see the camels coming up behind you, you're in danger of being cut off for being too slow. 'In the second-to-last push of the race I was only just in time - by 13 minutes.' Sir Ranulph received medical treatment at the end of the fourth stage of the race yesterday because the exertion had begun to take its toll on his heart. He was forced to lie down intermittently during the last few hours of the run because of fears he would not be able to finish the stage and described the experience as 'more hellish than hell'. As well as a double bypass, he has previously undergone a cancer operation and is in an ongoing fight with diabetes. Fundraising: Sir Ranulph's has raised almost £1million for Marie Curie, previously raising £6.3m the charity . Sir Ranulph is pictured here with his trainer Rory Coleman who at one stage repeatedly pushed the explorer to the ground for a rest before picking him back up again . Medical attention: Sir Ranulph Fiennes, 71, was taken to the medical tent because of concerns for his heart . Sir Ranulph, speaking after becoming the oldest Briton to complete the race, said: 'I got told by the surgeon when I had my last heart attack that I must not go over 130 heart beats a minute or undergo stress or extreme circumstances. 'When I get back to the UK I'm going straight to my surgeon to see what's gone wrong. 'I've not been in hot stuff on foot before and it's very, very difficult. 'The aim is to raise more money for more nurses in the UK with the wonderful Marie Curie, who make life much more bearable in a difficult time in your life.' Speaking after completing the race, he said: 'The main thing is this race is not set for old geriatrics like me' Sir Ranulph is pictured here with his trainer Rory Coleman who helped him to finish the gruelling fourth stage . There were fears he would not finish this stage of the race, but he was helped by his trainer Rory Coleman . Sir Ranulph has previously raised £6.3m for Marie Curie - in 2007 he climbed the Eiger mountain in the Bernese Alps by its infamous north face and in May 2009, at the age of 65, he became the oldest Briton to climb to the summit of Mount Everest. Dr Jane Collins, chief executive of Marie Curie said: 'We'd like to say a huge congratulations and thank you to Sir Ranulph Fiennes. 'It was clearly an incredibly difficult physical and mental challenge and he proves that with sheer determination, anything is possible.' To support Sir Ranulph and donate to Marie Curie Cancer Care, visit www.justgiving.com/ranulph. As well as a double bypass, he has undergone a cancer operation and is in an ongoing fight with diabetes . He said the work of Marie Curie Cancer Care nurses, who are also working through the night, keep him going . There were fears Sir Ranulph would not be able to finish the event after the 91km fourth stage, when he ran for more than 30 hours in temperatures topping 50C having had just one hour of sleep .
target: Sir Ranulph Fiennes is the oldest Briton to complete Marathon des Sables .
  Veteran explorer, 71, said the 256km race isn't set for old geriatrics like me'
  He has raised almost £1million for Marie Curie by completing six-day event .