An ice swimmer will walk the length of Hadrian's Wall dressed only in a small pair of trunks and a Roman helmet.
John Myatt decided to tick the walk off his bucket list after a family holiday was cancelled due to Covid-19.
He begins the challenge on Friday and aims to complete a 73-mile route along the monument within four days.
Mr Myatt said he originally planned to wear more conventional clothing but a friend told him to make it more challenging.
The father-of-three, from Gloucester, dropped out of a holiday to Norfolk due to the restrictions on groups larger than six mixing.
But rather than sit at home with a week off, he decided to take on a challenge at the Roman wall to raise money for the forces charity Rugby for Heroes.
"I thought why not tick something off the bucket list and Hadrian's Wall seemed like a good idea," he said.
Mr Myatt said he hoped his choice of attire would attract more people to donate.
"I was going to wear shorts and a T-shirt but my friend said I should wear trunks and make it more challenging," he added.
Mr Myatt is no stranger to combating cold temperatures and took part in the International Ice Swimming Championships in Russia in 2019.
He competed for Great Britain and acclimatised ahead of the event by swimming in a lake at the Cotswold Water Park and plunging into the ice bath he keeps in his back garden.
"I swam to France and back in 2018 and that led to swim for Great Britain in an ice swimming championships where I ended up winning gold," he said.
"I had to swim 1,000m at zero degrees as part of that."