Twenty-six miles and 385 yards. 42,195 metres. Some 55,000 steps. However you judge it, a marathon run is one of endurance sport’s ultimate tests. Yet for some runners, the iconic distance just isn’t enough, and they need to make things longer, higher and tougher.
Enter the ultra marathon, currently being undertaken by the former Made in Chelsea star and Radio 1 presenter, Jamie Laing, for Comic Relief. Laing is set to run 150 miles from London to Salford in Manchester over five days this week.
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How long is an ultra marathon?
An ultra is anything longer than a standard 26.2-mile (42.2km) marathon, with regular ultra distances including (and apologies for the switching between imperial and metric – race organisers and runners use the metrics interchangeably) 30 miles, 50km, 100km, 100 miles to over 200 miles.
What surfaces do ultra marathons take place on?
As anyone who has completed the road-based London, Manchester, Berlin or New York marathons will tell you, completing 26.2 miles on foot is a remarkable achievement. Yet ultra marathon courses regularly take things up a notch or three by taking place on off-road and often technical trails, away from tarmac and into the remote hills and mountains, where crowd support is minimal and aid stations are often absent.
Register for an ultra and say hello to boulder-strewn descents, grassy trails, exposed mountain paths, muddy banks and more, all at the mercy of changeable weather conditions. The elevation gain per mile is also ramped up, with some of our tough contenders below having 10km of climbing over their relentlessly rolling routes.
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What are the UK's toughest ultra-running marathons?
The UK has some formidable ultra-running events. Here are some of the toughest and most varied ultras in Britain for 2025, with some brutal alternatives from around the globe also below.
Dragon’s Back Race
Conwy to Cardiff; 236 miles (380km); 16,400m of ascent
Two hundred and thirty-six miles. Yep, you read that right. And that’s before we mention the 16.4km of climbing of the infamous Dragon's Back Race ultra-running test that runs the length of mainland Wales from Conwy to Cardiff from 1-6 September 2025.
The six-day challenge (a half version is also on offer) has an average daily distance of 39 miles (63km), which is close to a marathon a day, with competitors given from 6am until 10pm to run/walk/shuffle the daily distance before the overnight campsite. No outside support is allowed, while around 22% of the underfoot terrain is on pathless mountainsides (and there’s plenty of technical stuff in the other 78%). Throw the unpredictable Welsh weather into the mix and you can see why many think this is the UK’s toughest ultra-running challenge.
Montane Summer Spine Race
Edale to Kirk Yetholm; 268 miles (431km); 10,732m elevation gain
The Pennine Way from the Peak District to the Scottish border is Britain’s classic National Trail; 268 miles (431km) of remote uplands and some of the natural wonders of England. Expect to take 15-20 days to walk it. For the time-poor and athletically gifted, however, there is another option.
The non-stop Montane Summer Spine Race (15 June) has garnered a reputation as Britain’s toughest ultra running event and one that demands runners finish the trail in just 156 hours (6.5 days). The route starts in Edale in the Peak District, before runners traverse the national parks of Yorkshire Dales and Northumberland to reach the remote village of Kirk Yetholm in the Scottish Borders. Some 10,732 metres of ascent will need to be sprinted, shuffled or crawled over the duration, and it’s all unsupported, so participants need to sort sustenance and shelter themselves.
If a 268-mile run isn’t your bag, there are shorter options on offer throughout the Montane Summer Spine’s weekend, including the ‘Sprint South’ option: merely 46 miles with an 18-hour time limit.
Bob Graham Round
Keswick, Lake District, Cumbria; 66 miles (106km); 8,229m of ascent
The notorious 66-mile ultra-running challenge of the Bob Graham Round in the Lake District has no set day, but runners must register beforehand. And then finish the brutal circuit of 42 of the highest peaks in the Lake District within 24 hours.
The route was first completed back in 1932 by Bob Graham, a hotelier in Keswick, at the age of 42 and the 42 Peak Round has since become an ultimate test for Britain’s ultra runners. Only 100 experienced fell runners attempt the 8,229m of climbing each year, and only one in three of those make it back to Keswick’s Moot Hall before the clock ticks past 24 hours.
Race to the Stones
Lewknor to Avebury; 62 miles (100km); 1,342m of ascent
Another National Trail-inspired run is Race to the Stones (held on 13-14 July in 2025) from Threshold Events, which takes you through 5,000 years of history by following the Ridgeway National Trail for 62-miles (100km) from Lewknor to the UNESCO World Heritage Site at Avebury and its standing stones.
Top 50km options are on offer, but the most popular course is the full 62-mile option, which can be taken on non-stop or over two days by staying in the event’s basecamp along the way. The winning time in 2024 was under eight hours, while the last finisher walked home in 30 hours. At 1,342m over the 62 miles, the elevation gain isn’t outrageous, but the sheer distance, off-road terrain and potential midsummer heat (or rain on the Ridgeway’s slippery chalky trail) are all factors that entrants need to consider.
Two Tunnels Ultra
Bath, Somerset; 31-miles (50km)
For those of you not needing a vitamin D hit, the Two Tunnels Ultra is a 31-mile (50km) run in the titular tunnels in Bath, Somerset, on 17 August 2025.
The route might be flat, the underfoot terrain in good nick, but the consistent time (around 20 of the 50 kilometres) in the long, dark, chilly and potentially claustrophobic tunnels will test many runners’ mental resolve to the limits. The race goes through the Devonshire Tunnel (408m) and the Combe Down Tunnel (1,672m), which is the longest underground section in a UK running race.
Both a relay and an option for pairs to share the miles are also on offer, as well as a host of shorter events on the day. (There’s also a 200-mile ultra through the tunnels in March 2026, run during the night and purely in the tunnels).
The world's toughest ultra marathons
It might not be the longest, but the circa 100-mile Barkley Marathons in Morgan County, Tennessee, is oft-cited as the world's most brutal ultra-running event due to its unmarked course of five loops of roughly 20 miles where entrants face thick forests and dense vegetation on a route that changes every year. And one so tough that there are regularly no finishers.
With 160 miles (250km) spread over seven days and 2,788m of elevation gain, Morocco’s Marathon des Sables in the Sahara Desert might not rank as highly as the ultra competition in terms of stats. But the key number to note is that daytime air temperatures can reach 50ºC in the Sahara. And that's before we mention the leg-sapping sands, winds, sandstorms, navigational issues and having to carry your own supplies for the entirety.
The Badwater 135 tests runners with 135 miles and has 4,450m of elevation gain over a 48-hour period. The road-based nature of the terrain makes it a complete contrast to Barkley, but the searing, shoe-melting desert heat of California's Death Valley in July, as well as travelling from the USA's lowest point to one of its highest, make it legendary in ultra circles.
Main image credit: BBC Radio 1 presenter Jamie Laing (centre) during day three of his 2025 Comic Relief challenge/Getty
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