Abseiling down a 140ft waterfall, riding rapids in Costa Rica, and taking on the world's fastest water-slide in Dubai, might sound like an adrenaline junkie's ideal adventure.

But, for 78-year-old grandmother Ann Berg, it was a way of showing her family and friends it is not just young people who can take on a new challenge.

Mrs Berg, from Golders Green, north London, is one of four senior citizens, who star in the Sky One series, 50 Ways to Kill Your Mammies, a show that takes them around the world to carry out daredevil stunts.

The grandmother-of-two, who typically spends her days "to-ing and fro-ing between home and Sainsbury's," said having to run away from cheetahs in the wild was "quite different" to walking quickly to catch a bus.

She admitted: "I got into the show by complete accident. I'm not the kind of person who does that sort of thing.

"Even if I go swimming I desperately try to keep my hair dry. My children think it is hilarious."

The widow moved back to London from Boston in the United States two years ago, after losing her husband to cancer. She said: "My daughter's friend noticed an advert for a free holiday and said: 'Why don't you phone up and find out what it is about?'

"Innocently, I rang up because I really needed a holiday and since I lost my husband I can't really afford to go to faraway places."

But Mrs Berg originally rejected the Sky producer's offers to take part in the Emmy award-winning show, now in its third series. She said: "When they told me what I'd have to do, I said: 'Oh no thank you, sorry, I can't do that.'

"But they called me back and said they really wanted me to be in the show. I couldn't believe it and, because they were so nice to me, I thought, 'why not?'"

Despite never doing "anything adventurous" before, the grandmother can be seen conquering some of her biggest fears on the show, which airs every Monday on Sky One at 9pm.

Mrs Berg, a member of the Liberal Jewish Synagogue, revealed: "In one of the last episodes, I got to go to Uganda and you'll see producers tell me I have to drive this commuter bus out of a muddy swamp.

"It was indescribable. You won't believe it. I was in a crowded, muddy bus station surrounded by thousands of other buses and I had to drive it with passengers inside. There are no traffic lights or anything. I just got in it and went. It was so dangerous."

Mrs Berg, who worked as a lawyer's assistant before she started a family, said driving the bus scared her more than driving a Lamborghini at full speed or being locked in a cage with chimpanzees, both of which she has done on the show.

She said: "The whole time, I just kept thinking: 'I'll never have another opportunity to do this, I have to go for it all.'

"I wanted to show old people are not down and out because we reach a certain age. We can do anything we want."