An international field of almost 200 runners is expected to start an extreme challenge in the Scottish Highlands.
The Cape Wrath Ultra Race starts at 10am on Sunday, with competitors facing 11,200m (36,745ft) of ascent over the 400km (249-mile) course.
Runners from 23 different countries are expected to take up the challenge of an eight-day expedition into some of Scotland’s wildest country. The race runs from Fort William in Lochaber to Cape Wrath in the far North-West.
Twenty-one Scottish runners are also in the start list for the race.
The route of the Cape Wrath Ultra is based on the long-distance Cape Wrath Trail. The average time to walk the trail is three weeks, but the ultrarunners will have just eight days to finish, with strict cut-off times.
The route includes more than 100 river crossings.
The event has only been run once before. The team behind the biennial race also organises the Berghaus Dragon’s Back Race in Wales, with which the Cape Wrath Ultra now alternates. There are double the number of entrants from when the Scottish race was first staged.
Among fancied runners in the 190-strong field are Jim Mann and Carol Morgan, both winners of the Berghaus Dragon’s Back.
Race director Shane Ohly said: “The Cape Wrath Ultra is an extreme challenge with runners crossing some of the wildest and remotest terrain in the UK.
“It’s not a route designed to cross or climb mountains but to take the natural line through the mountains. We have created a logical route dating back to ancient times.”
Organisers said completion of the race requires dedication to training, endurance, self-reliance, navigational skills, confidence and self-belief. Yet even then it will test the toughest of competitors.
During the last event, in almost perfect weather, more than a third of participants did not finish.
The 2016 female race winner Ita Emanuela Marzotto of Italy, said it was ‘the hardest thing I’ve ever done’. She added: “It was tougher than the Marathon Des Sables.”
Runners’ progress can be followed via the Open Tracking website.