Sir Ranulph said the marathon had been "good fun"
British adventurer Sir Ranulph Fiennes has told of his joy at completing seven marathons on seven continents in seven days.
The 59-year-old said the Singapore run in tropical heat had nearly broken him because of the difficulty of continuing in the humidity and pollution.
But he and his fellow runner Dr Michael Stroud went on to complete the challenge to run 183 miles in just a week.
Sir Ranulph told reporters in London on Monday it has been "absolutely wonderful" to finish.
He ended his marathons with a race in New York which he finished in five hours and 25 minutes on Sunday at 2030 GMT.
The pair had already completed runs on the Falkland Islands, Santiago in Chile, Sydney, Singapore, London and Cairo.
But Sir Ranulph recalled how the Singapore marathon had stretched him almost to breaking point.
He said: "I hit the pavement and nearly fainted at the end.
"I felt completely knackered and not able to do another one."
Dr Stroud walked much of the way after suffering a stomach upset.
Sir Ranulph's personal achievement was all the more remarkable given the punishing jet lag he must have suffered after arriving in a city almost a full working day behind the Middle Eastern time zone.
He said he would like to drink hot chocolate and eat chicken masala.
"Anything without cholesterol in it," added the veteran adventurer who recently underwent heart surgery - and who was raising money for a heart charity.
Sir Ranulph has fought back from a heart attack and a double heart bypass operation to carry out his latest test of endurance.
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.