Tim Ralph, 53, is in training to climb Mount Vinson to raise money for the charity, where he works with visually impaired youngsters.

When the experienced mountaineer reaches the 4,897m summit he will have scaled the highest mountains on six of the seven continents – known as the Seven Continental Summits – with just Mount Everest left to conquer.

The father of two has taken to dragging a tractor tyre around the streets of Harrogate to simulate the weight of a sled.

To further improve his fitness, he is pulling the tyre while walking on skis fitted with wheels.

He said: "This is the final mountain to ascend before I take on Everest and complete the set of seven.

"I have been climbing for twenty years but only decided to start tackling the globe's highest mountains when a friend gave me an inspirational book listing things to do before you die.

"I started with Kilimanjaro five years ago and have scaled a further five of the continental summits since then."

His recent climbs include the 6,194m high Denali in Alaska and the 6,969m Aconcagua in South America.

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