A council worker from Cardiff is helping explorer Sir Ranulph Fiennes prepare for his latest expedition - a charity ascent of Everest.
Hadyn Griffiths shows Sir Ranulph Fiennes the ropes
Structural engineer Haydn Griffiths was recommended to Sir Ranulph, 61, to teach him how to rock climb.
The adventurer is climbing the mountain's north face next month - despite his fear of heights - to raise £2m for the British Heart Foundation.
Mr Griffiths is a member of the South Wales Mountaineering club.
He said he was called up by Sir Ranulph, who "very politely asked if I could teach him a few things about rock climbing".
"I have taken him down the Gower a couple of times, quite locally up at Taffs Well at the cliffs below Castell Coch and we have been to the Avon Gorge a number of times and the Wye Valley," he said.
"He is very very good - for someone who only started climbing last summer, he is doing extremely well."
However, he said he would not be accompanying Sir Ranulph on the trip.
"I've not done Everest and I have no intention of doing it either," he said.
Sir Ranulph said he had got Mr Griffith's number from other climbers.
"A lot of people all over the UK know each other in the rock-climbing community," he said.
He added that, because he comes from Somerset, his contacts thought Cardiff would be near and that "the best guy there" was Hadyn Griffiths.
Sir Ranulph described Mr Griffiths as "just brilliant" and said he watched in amazement as his teacher climbed above him.
Sir Ranulph Fiennes has conquered the South Pole
"Watching from below, I then try to get up what he has got up, and it looks totally impossible," he said.
"How the hell he gets there is beyond me."
He added that, as he learned the hopes, he had "total confidence" in Mr Griffiths.
Sir Ranulph had a heart attack in 2003 but months later broke records by completing seven marathons on seven continents in seven days.
He is raising money for the charity which helped pioneer research which had helped him survive the attack.
"This Everest climb is for a specific unit in the Great Ormond Street Children's Hospital to concentrate on the growing amount of heart disease in six and seven-year-olds," he said.
In 1993, Sir Ranulph and Dr Mike Stroud became the first men to walk unaided across the Antarctic continent.
Seven years later, severe frostbite dramatically halted this attempt to reach the North Pole after he plunged into freezing water when one of the two sledges he was towing fell through thin ice.