Blue Peter action woman Helen Skelton is hoping to prove she has a head for heights by walking a tightrope between the chimneys of Battersea Power Station.
If she succeeds, the 27-year-old would become the first person to high-wire walk the 150-metre length of the iconic south London building.
Skelton has secretly been in training for the Red Nose Day charity challenge for several months.
She will be 66 metres up and holding an eight-metre long balance pole in front of her when she attempts the feat on the 18mm-thick piece of wire at the end of the month.
The BBC children's television presenter said she was inspired by the documentary Man On Wire, which shows Frenchman Philippe Petit walking on a tightrope between the twin towers at New York's World Trade Centre towers in 1974.
Skelton, who became the first person to solo kayak the Amazon in an earlier stunt, said: "I was so impressed when I saw the film that I said 'Wouldn't it be amazing to do something like that'. I didn't think about how heavy and difficult it would be to hold the balance pole out in front of me for so long.
"I knew it would be scary and a challenge to stay focused but I really hadn't realised how physical it would be. I am covered in bruises from falling on the wire - which is incredibly painful.
"It has been hard work but that's what is going to make me grit my teeth and keep going when my arms burn. I only hope I can hold my nerve and keep my eyes on the wire - if I stay focused I'm sure I can make it across."
A safety device that the presenter described as being "like a seatbelt" will be attached to her in case she falls, but she will be unable to feel it while walking on the wire.
Skelton, whose wire-walking will be shown on future episodes of Blue Peter, said: "Doing it at Battersea means my family can come and watch, which is great for me but pretty stressful for my mum."