The event dubbed Britain’s most brutal race got underway on Sunday morning with runners having to contend with typical Pennine winter weather.
An overnight thaw meant competitors in the Montane Spine Race faced footpaths that had turned into streams as meltwater ran from the Peak District hills.
More than 100 ultrarunners made the start from Edale with the international field including past winners Eoin Keith and Pavel Paloncý. Thirteen women began the race, which follows the full 420km (268-mile) length of the Pennine Way national trail.
The field has been running for more than 12 hours and is heading north through the night after a day spent in drizzle and poor visibility. Lead runners Irishman Eoin Keith and Czech Pavel Paloncý had a short lead over third place man Eugeni Roselló Solé of Spain as they headed over on to the Brontë moors in West Yorkshire. The trio swapped lead for most of the first day of the race.
Leading woman runner is Carol Morgan of Ireland, who arrived at the M62 checkpoint in joint seventh overall place as night fell.
There have been five retirements from the Montane Spine Race so far.
The shorter Montane Spine Challenger Race, which ends at Hawes in the Yorkshire Dales after covering the southern109 miles, was won by Dominic Layfield in a provisional new course record of 28hrs 4mins 28secs.
Alasdair Cowell looked set to win the Montane Spine MRT Challenge for active members of mountain rescue teams as he approached the Hawes finish with a seemingly unassailable lead over Andy Jackson.
The inaugural Spine Race first took place in 2012 with only 11 entrants, of which only three ultimately crossed the finish line. Since then, the race’s notorious brutality has attracted competitors from around the world, attracting new racers each year who seek the next scalp on their endurance race hit list.
A set of stringent entry criteria ensures athletes do not enter ‘on a whim’ and are fully cognisant of the enormity of the undertaking.
Competitors in the longer race must complete the course, which involves 13,135m (43,094ft) of ascent, in no more than 168 hours. The Challenger course has 5,637m (18,494ft) of ascent and a time limit of 60 hours.