He is no stranger to endurance challenges but nothing prepared Paul Parrish for what lay ahead when he took part in the hit BBC2 series Special Forces: Ultimate Hell Week.

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Not only did the 29 participants face sleep deprivation, hunger and cold, they were also bawled out by military strongmen and tested at every turn.

But to his credit father-of-three Paul, 50, who lives in Wheathampstead, made it to the fifth episode of the six-part series and was the last - older man - standing.

And he even admits to missing certain aspects of the reality show, fronted by cricket legend Freddie Flintoff, which tested its participants to their physical and mental limits in a 12-day period in May.

Paul, a former journalist who was, by his own admission, overweight and unfit, is now director of fundraising and marketing for the charity Aspire.

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His fundraising activities in Ironman events were capped last year when he completed the Arch to Arc Challenge, regarded as the world’s hardest triathlon.

Becoming only the 20th person to complete it since it began in 2001, it involved an 87-mile run from Marble Arch to Dover, a solo swim of the English Channel and then a 180-mile cycle ride to the Arc de Triomphe.

It was that type of endurance challenge which prompted him to apply for the show when friends sent him application forms for it. At first reluctant because of the military connotations, he decided to go for it because the programme-makers were asking for interesting back stories.

Over 1,000 people applied for the show and he had to undergo an assessment weekend in March. At first Paul was told he had not been selected but only days before filming began, he got a call to say that the show’s medical team, whom he knew from triathlons, had recommended he should take part.

And that is how he found himself in Newport, Wales, with a group of men and women of various ages - at that time he was the fifth oldest participant - none of whom really knew what to expect.

What they soon discovered was that they would be undergoing special forces selection tests devised by the military from across the world including NAVSOG from the Philippines, the American Navy SEALS, Israel’s counter-terrorist unit Yamam, the Australian SAS and Russia’s Spetnaz.

Six participants did not make it past the first few hours with the SEALS but Paul stood up well to being immersed in freezing sea water, pack races, sit ups and press ups - all of which was accompanied by hunger and sleep deprivation. He said: “We were woken up at 1am, hosepiped and drilled, then taken on a two and a half hour journey to the coast. We got there at about 5.30-6am and didn’t leave until 6pm.”

His low profile didn’t last long - by episode three when the remaining participants were in the hands of NAVSOG, he found himself in the line of fire.

His leadership skills were criticised and undermined, his lack of pace was apparent and he thought his time was up. He saw the effect of sleep deprivation on one of his colleagues who was hallucinating and was sent home.

Paul was sure he would be joining him but in the event, the willingness of the remaining participants to keep on going was ‘rewarded’ by being allowed to remain.

But Paul knew he was living on borrowed time and he finally parted company with the six-part series in episode five when he came in last in a pack race. By then he was the oldest competitor remaining,

Only three went on to compete in the final and by then, according to Paul, they had ‘gone 12 days with three to four hours sleep a night.”

The ultimate winner was Clare Miller, a hospital doctor who was one of a handful of women to take part in the show.

Paul stood out from many of the others because he treated the experience with his usual good humour. He explained: “Because it became so ludicrous, it was impossible to take it very seriously.”

He had the utmost respect for his colleagues and that was clearly reciprocated as they urged him on in his final episode even though he knew his time was up. Even a couple of the instructors seemed to warm to him.

Two tasks stick in his mind that he did not relish - having to fight other contestants and pushing a landrover out of the thick Welsh mud which, with the lack of leadership, reminded him of management training courses in the business world.

And the best part? Arriving back at the four-star hotel in Newport after he was sent packing to find a kettle and mug waiting for him. “I have never enjoyed a cup of tea so much,” he confessed.

Paul got back home on the Saturday and was back at work on Monday but was unable to tell anyone how he had done. He has no regrets and would never rule out doing something like it again - not just because of the ‘lovely’ people he met but because of the ‘more interesting texture to life’ it gave him.