The 10 UK races with the highest DNF rates

Not every race is meant to be finished. Some events are deliberately designed to test the outer limits of human endurance, where being fit isn't enough to guarantee you'll see the finish line.

We analysed over 120,000 race results across 318 UK events in our database to find which races have the highest DNF (Did Not Finish) rates. DNF rate is calculated as the percentage of starters who didn't finish, using only participants recorded as either FINISHED or DNF (DNS entries are excluded). Only races with at least 50 starters in our data are included.

Some of these results will surprise you.

The 10 highest DNF rate races

1. UTS 165 — 65.2% DNF

92 starters analysed · 2021

The 165km course at Ultra Trail Snowdonia is the hardest-to-finish event in our database. In 2021, fewer than 35 in every 100 starters made it to the finish line. The race sends runners through the heart of Snowdonia's mountain terrain on a course that combines technical ridgeline running, extreme elevation change, and time cutoffs that leave almost no margin for error. It demands near-perfect execution on some of the most demanding ground in Wales.

2. Montane Spine Challenger | MRT — 60.3% DNF

214 starters analysed · 2022–2023

The Spine Challenger covers around 108 miles from Edale to Hardcastle Crags along the Pennine Way. The MRT (Montane Race Team) category removes supported crew access and pacing, meaning athletes are essentially racing self-supported through January conditions on exposed Pennine moorland. Navigation, weather, and accumulated sleeplessness account for the majority of withdrawals. Across two years of data, 60 in every 100 starters didn't finish.

3. 13 Valleys Ultra — 59.4% DNF

192 starters analysed · 2025

A relatively recent entry in the race calendar, the 13 Valleys Ultra earned its place on this list fast. In 2025, nearly 60% of starters didn't make it to the finish. The name tells you what to expect: relentless climbing through valley after valley in the Welsh mountains, where each descent simply delivers you to the bottom of the next ascent. More years of data will tell us whether this attrition rate holds.

4. Dragon's Back Race — 52.3% DNF

1,316 starters analysed · 2017–2025

The Dragon's Back Race is one of the most famous ultra events in the world. Over six days, runners traverse 380km along the mountainous spine of Wales from Conwy Castle in the north to Cardiff Castle in the south. With over 1,300 starters in our database across five race years, the 52.3% DNF rate is one of the most statistically reliable on this list. There is nowhere to hide on the Dragon's Back. Technical terrain, daily time cutoffs, and cumulative fatigue claim a majority of the field every single year.

5. C2C in a Day — 51.6% DNF

1,925 starters analysed · 2018–2022

Wainwright's Coast to Coast covers around 190 miles from St Bees on the Irish Sea to Robin Hood's Bay on the North Sea. Completing it in a single continuous non-stop push is one of British ultra running's most extreme undertakings. With nearly 2,000 starters across three years in our data and more than half not finishing, C2C in a Day demonstrates that even a well-established long-distance route becomes a different beast entirely when stripped of multi-day rest.

6. Devon Coast to Coast — 50.0% DNF

52 starters analysed · 2021

Exactly half of every starter in our data didn't finish the Devon Coast to Coast ultra. The sample is small enough that this rate should be treated with caution, but the pattern is consistent with what we see across multi-day and point-to-point events. Devon's terrain holds more challenge than the county's rolling reputation suggests, and 2021 conditions appear to have made this edition particularly brutal.

7. Hardmoors 110 — 47.2% DNF

214 starters analysed · 2024–2026

The Hardmoors series produces consistently tough races, and the 110-mile route along the Cleveland Way and the North Yorkshire Moors coast path is no exception. Nearly half of all starters across the last three editions didn't finish. The race runs in January, facing full North Sea weather and exposed moorland. Cold, wind, and mud compound over the course of 110 miles to create conditions where even well-prepared runners find themselves pulling out before the finish.

8. Summer Spine — 46.2% DNF

91 starters analysed · 2021

The Summer Spine covers the full 268-mile Pennine Way from Edale to Kirk Yetholm in a single non-stop push. Despite the name suggesting easier conditions than the January Spine Race, the summer edition is simply a different kind of brutal. Heat, extended daylight, and the relentless nature of the Pennine Way mean that nearly half the 2021 field didn't reach Scotland. This remains one of Britain's defining endurance challenges regardless of the season.

9. Cape Wrath Ultra — 45.9% DNF

1,111 starters analysed · 2016–2025

Cape Wrath Ultra is a multi-stage race through the Scottish Highlands, finishing at the remote Cape Wrath lighthouse at the most northwesterly point of mainland Britain. Across seven years of results in our database, 45.9% of starters didn't complete the event. The race covers approximately 400km of some of Scotland's most remote and pathless terrain, with bog crossings, mountain ridges, and river fords in all weathers. The attrition rate is remarkably consistent year on year, which tells you this isn't a bad year problem. This is just what the race is.

10. Montane Spine Challenger South | MRT — 45.8% DNF

312 starters analysed · 2024–2025

The southern variant of the Spine Challenger runs the lower half of the Pennine Way from Hardcastle Crags to Edale in the MRT (Montane Race Team) self-supported category. Roughly 100 miles in January across the gritstone edges and boggy moorland of the Dark Peak plateau. Just under half of all starters across 2024 and 2025 didn't finish. Shorter than its northern counterpart, but in winter conditions on the exposed southern Pennines, every mile counts.

What these numbers tell us

Winter non-stop events dominate. The Spine Race and its variants appear three times in the top 10. Running through January on exposed moorland, non-stop and largely unsupported, is a genuinely different category of challenge from even the hardest point-to-point summer races.

Multi-day accumulation is its own problem. The Dragon's Back Race, Cape Wrath Ultra, and C2C in a Day are all events where the challenge builds across days. Small problems compound. A blister that would be manageable in a 50-mile race becomes catastrophic by day three of a stage race.

Remote terrain is not the same as difficult terrain. Several of the highest DNF events take place on ground that isn't technically hard to run, but that offers no escape routes, no drop bags, and no reliable shelter. When things go wrong in the Scottish Highlands at 2am, the consequences are different from going wrong at mile 40 of a marked trail race.

A high DNF rate isn't a mark against a race. Many of the events here are among the most respected in British ultra running. They're hard to finish because they are genuinely, intentionally hard, and that is exactly what draws athletes to the start line every year.