Derek Grosvenor (55), who works for British Gas, and Tim Miles (63) have been friends for 25 years, and will walk from Aviemore to Fort William to raise funds for Shelter Scotland.

The pair will experience the beauty, and challenges, of Cairngorms National Park, a remote pass between the Munros of Ben Alder (1148 mtrs) and Aonach Beag (1116 mtrs) ,while descending the Steall Gorge beneath the Ben Nevis massif, on their five day 70 mile trek. They will cover an average of 15 miles a day on foot.

Both men have been training every weekend since March covering a total of 200 miles in a bid to prepare for the challenge, and raise £2,500 – enough to help 250 families though Shelter Scotland’s free national helpline.

Derek Grosvenor, a British Gas energy efficiency employee from Northampton, said: “We’ve been friends for a long time and have always loved coming up to the Scottish Highlands. On previous trips we were taken aback at the scars left by the Highland Clearances and the impact those evictions had on the lives of entire communities who lost their homes.

“We knew we wanted to raise money for a charity that helps people keep their homes, so we naturally thought of Shelter Scotland.

“We’re excited by the prospect of spending almost a week in the wild. We know it will be a challenge, but it will be nothing compared to the hardship faced by tens of thousands of families across Scotland who don’t have a house to call their own.”

Derek said he was also inspired to raise money for people in housing need after working with social housing tenants and landlords in the West of Scotland through the British Gas Heat Networks scheme which aims to improve energy efficiency in homes. Through his work, Derek said he has seen the positive impact good homes can have on individuals, families and communities as a whole.

British Gas and Shelter have a five-year partnership which aims to help improve standards of 1 million homes in the private rented sector across the UK.

During the challenge Derek and Tim will carry a week’s worth of supplies, including food, a tent, gas burner, sleeping bags and clothes. They say their biggest luxury will be a travel towel.

Tim Miles, who met friend Derek on a Winter climbing trip to Glencoe at Christmas in 1990, said: “Our training sessions have been long and hard in some of the worst Spring weather imaginable. While on a training trek in the Lake District we discovered the newly purchased travel towels were both a luxury and essential at the end of a long hard day, for mopping up the perspiration and rain water in equal measures.

“We’ve also had a lot of time to reflect and realise that a home is one of the most important things in our lives. Having a place to call your own is easy to take for granted, until you no longer have it.”

Alison Watson, deputy director of Shelter Scotland, added: “I am in awe of Derek and Tim’s determination and generosity. At a time when funding for our vital services is under ever increasing pressure, people like them make a real difference.

“We are humbled that Derek and Tim have chosen to raise money for Shelter Scotland. Donations like this go a long way and help us in our work to end Scotland’s housing crisis for good. We wish them the best of luck as they embark on their adventure.”

Derek and Tim will arrive in Scotland today before embarking on their adventure on Sunday. They aim to complete the challenge in five to seven days.

Donations can be made here.