Ross Jenkin will on Sunday begin a "Big 4 Grand Round" attempt, trying a continuous traverse of all four of the national 24-hour mountain challenges.
He will start with the Ramsey Round in Scotland, before moving on to the Dennis Rankin Round in Northern Ireland, the Paddy Buckley Round in Wales and finally the Bob Graham Round in England, resting only on the travel legs in between.
The Dynafit-sponsored athlete, who is raising funds for CALM (Campaign Against Living Miserably), would need to complete 152 summits, 387km and 31,800m of ascent to be successful.
He had to abandon an attempt on the Grand Round last summer due to an ankle injury.
So far Jenkin has raised nearly £7,000 and is aiming for £15,000. “The power of the mind is immense. I can safely say that I am stronger now than I was before all this. Don't man-up, speak-up!” he said.