The One Show presenter Alex Jones is to spend three days climbing a US mountain to raise funds for Sport Relief.
The host will scale the vertical Moonlight Buttress in Utah's Zion National Park, which is 1,200ft (365 metres) tall.
Jones, who has no climbing experience "except for the odd tree", said it was a "daunting" prospect.
Viewers of the BBC One programme will be able to watch her progress from 17-20 March.
They are being asked to sponsor Jones' effort to raise thousands of pounds for good causes.
The Welsh presenter, who has spent three months intensively training for the climb, said: "I can't quite get my head round hauling my body weight up one of North America's tallest vertical rock faces.
"I'll also have to try and master suspended sleeping and the delicate issue of 'toilet etiquette', but the thought of helping those in need will get me through."
Jones added that she was "compelled to say yes to the challenge" despite her lack of experience.
The effort of hauling herself up the vertical rock face and clinging on to its surface will lead Jones to burn around 700 calories an hour.
TV presenter Davina McCall recently completed a seven-day, 500 mile endurance test which culminated with a marathon run.
Her efforts have raised in excess of £700,000 for Sport Relief.