It is a gruelling outdoor challenge that pitches participants against nature and the elements to cross some of the most stunning hills and glens in the Highlands.
Around 1,000 people are to take on the Caledonian Challenge in June, with the goal of raising half a million pounds for charity.
To do so they must cover most of the northern part of the West Highland Way in record time.
For 2015 there are two events, The 54 and or The 24. The 54 involves covering that number of miles in 24 hours. Participants have 12 hours to complete the 24- mile route.
Entrepreneurs Angus MacDonald and Alex Blyth founded the Caledonian Challenge in 1996. Inspired by an event in Hong Kong, the pair wanted to run an endurance event in the Highlands.
The first challenge was to complete 30 Munros - mountains over 3,000ft - in four days. Only two completed the whole course and £16,000 was raised for charity.
The next year saw the Caledonian Challenge move to the West Highland Way. Since then more than 17,000 people have taken part in it, helping to raise over £13 million for Foundation Scotland.
Established in 1996, it is Scotland's busiest grantmaker, making more awards to good causes than any other independent funder.
More than 250 individuals, families, charitable trusts, companies and public bodies now channel their contributions to good causes through the Foundation.
The 54 starts at Gairlochy, on the Great Glen Way walk north of Fort William, and ends at Strathfillan Wigams near Tyndrum. The 24 starts in Glen Nevis, ending at the Glencoe Ski centre.
On both, participants have to climb out of Glen Nevis, head along the Lairigmor - the great pass - to an old military road and then down into Kinlochleven.
They are then faced with a climb out of "the electric village" and over to the legendary Devil's Staircase path to take them down to Glencoe.
As preparations get under way to stage the Challenge, The Herald is delighted to announce its involvement in the event for the first time.
We will be following the build-up to the events over the next few months, highlighting the preparation of the teams, the training regime and where some of the money raised will be spent.
And to show our commitment The Herald will also be entering a team of hardy souls.
Organisers anticipate around 185 walking teams, although some will run, entering with each member raising at least £400 on The 54 and £300 on the The 24.
Foundation Scotland will distribute the money raised through the sweat, blisters and tears of the Challenge
Foundation chairman Tom Ward, an event veteran, said: "The Caledonian Challenge is firmly established as one of Scotland's favourite events.
"It offers a fantastic experience to the participants and their stalwart support teams - every year, we get over 98 per cent saying that they'd recommend it to their friends.
"Walking on long-distance footpaths through the West Highlands is unlike anything else you can do in the UK - something you'll never forget.
"But our real pride is the fundraising. For 2015 we have two events … which together should raise over £500,000 to support community projects in deprived areas of Scotland.
"For anyone wondering what they can put back into society, just look at some of the projects we support - facilities for disabled children; sheltered workplaces for those recovering from mental illness; social clubs for those with dementia - and you see what strengthening communities means in action. You can help make it happen."
Magnus Llewellin, editor of The Herald, said: "The Caledonian Challenge has already achieved so much in terms of fundraising, and The Herald is proud to support the event.
"But also the idea of 1,000 people heading to the hills to raise money for charity continues to strike a chord in Scotland.
"I know those taking part get something special - not just blisters and aching muscles - from the experience."
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