Helen Skelton: 'I heard these funny grunting noises. It was a group of crocodiles…'

Skelton says: 'A lot of people doubted I could run an ultra-marathon. I wasn't a runner but I wanted to prove I could do it.' (Getty Images)

You lose your identity when you join 'Blue Peter' When I joined as a presenter in 2008 I wanted to do something on the show that was about me, and would give people another reason to talk about me, which is why I took on challenges such as running an ultra-marathon.

The phrase 'here's one I made earlier' still slips in occasionally If I say it during the show one of the cameramen always clinks their tripod in recognition – some of them have been there a long time and they love it! But these days it's more about challenges and action, such as jumping out of planes.

A lot of people doubted I could run an ultra-marathon I wasn't a runner but I wanted to prove I could do it, so I entered the 78-mile Namibian ultra-marathon. I started by running for 10 minutes a day and built it up. A lot of people didn't think I could do it, including some there on the run: one guy said, "You won't finish it so you might as well just enjoy the view." It was all I needed to hear to get me up and going for the final 50 miles.

There are a lot of urban myths about the Amazon Like that you can get nibbled to death by piranhas. I saw a lot of crocodiles during my 2,000-mile kayak along the Amazon for Sport Relief in 2010, though. One night I was paddling along a stretch of river when I heard these funny grunting noises that caiman crocodiles make. It was a group of them, which was really intimidating, as they've a fierce bite. But if you shine a torch in their eyes they get stunned, and they freeze.

The South Pole is brutal Before I went on a trek there for last year's Sport Relief, I spoke to Ranulph Fiennes, who was telling me how sweat can cause hypothermia and how he lost his fingers there to frostbite. I think I was at my most depressed on Christmas Day, stuck in a tent during a blizzard for 48 hours and being away from my family. I felt quite disgusting as I'd also had to wear the same clothes, with no washing possible for two weeks – and I had a loose stomach from the dried-food Army rations!

Army rations taste horrible The freeze-dried muesli in particular is disgusting. It's such a faff to prepare, too. First you need to melt some snow and boil the water over a stove, then you open up the ration pack, add the water and leave for 10 minutes.

I can't go to sleep at night unless I've had an hour of fresh air I was brought up in a rural environment, and I'd often sleep in the back garden. So when I moved to London in 2007 I made sure I moved next to a park. But even then it was like, oh my god, even in Richmond Park you can see high-rise flats.

Helen Skelton, 29, is a TV presenter for 'Countryfile' and 'Blue Peter'. She holds a Guinness World Record for the longest solo journey by kayak, with 2,010 miles, which took her just over a month to complete. Last year she became the first person to reach the South Pole using a bicycle