The UK’s best iron-distance triathlons

Hoping to step up a distance or determined to beat your PB from the last full-distance triathlon you tackled? Here, we take a look at some of the best Ironman-distance triathlons you can tackle in the UK.

In years gone by, this list has been longer, but a number of events have ceased to exist in recent years. That said, there are still plenty for you to choose from, including these…

But first, if you need a recap on what an Ironman or full-distance triathlon entails, see our guide to the different triathlon distances.

Outlaw Nottingham Triathlon

Where: Holme Pierrepont, Nottingham, England
When: July

We named this event the most beginner friendly ironman-distance triathlon in Europe, despite the often not so friendly weather. Here’s previous finisher Jason Scott with some essential advice for your Nottinghamshire crusade…

Pre-race

I chose The Outlaw because I’d heard good things and it’s known for being considerably flatter than Ironman UK (which is not currently in operation). I’d say if you’re not signed up for an M-Dot event then this is the next (or arguably should be first) on your list of must-do long-distance races.

Myself and a friend camped on site, only 200m from transition. They also offer luxury wooden pods to stay in, which I’d recommend for extra comfort. Registration is a breeze the day before, and set-up is quick and no hassle.

The swim

The Outlaw swim is a proper Iron start. None of this small pens of starters at a time; it’s a mass underwater wrestle! If you’ve positioned yourself correctly according to your predicted time, though, you should be fine; it soon thins out. It’s one large lap, which is right to the end of the rowing lake and back again.

If it’s a sunny early morning, sighting on the swim can be quite difficult as the sun is low.Unless you’re flying at the front, just do as I did and follow the few hundred people in front of you!

The transition area is great, slick and easy to get through, and there are lots of great viewing spots around the lake for family and friends to cheer you on.

The bike

The bike course is a flat-ish 180km. It’s more rolling tarmac than anything else and a good average speed can be met quite easily.

You get some nice views of the Nottinghamshire countryside, and the course is three laps (laps one and three are the same), making it easy to mentally divide up.

The run

The run is a flat and well-supported route, which starts off with a lap of the lake and then continues along the River Trent. This is done twice before a final loop of the lake to finish off.

Walking through the aid stations helped me immensely, and my general Iron race tip would be to never stop completely and keep walking through.

There are plenty of feed points en route so plenty of chances to recharge your batteries. The great marshals are particularly appreciated towards the end of the run course when, although you’ve had a long day, theirs has probably been even longer!

For more information, check out the Outlaw Triathlon event website.

The Brutal Triathlon

Where: Llanberis, Gwynedd, Wales
When: September

With its huge amount of climbing and 16:50hr median finish time, we named The Brutal the 2nd toughest Ironman-distance triathlon in the world. But fear ye not Brutal entrants, here are the winning tips for Snowdonia success from previous winner David Chapman…

Pre-race

This is one tough race. Snowdonia will probably involve a fair drive to get to, so get this done sooner rather than later. Racking your bike the night before can help reduce grief on race day, or turn up early to secure a place in the small car park right by transition. Book somewhere to stay in Llanberis itself, that way you’re never too far from the race headquarters.

The swim

Llyn (lake) Padarn is famously cold. A neoprene cap really helps with warmth, and you can even use neoprene socks and gloves.

We’ve kicked off with a hard frost on the ground in the past but, even if it’s warmer, a decent run between swim exit and transition means it’s a good idea to bring an extra pair of run shoes.

Have a short warm-up before the deep-water start. It’s four triangle laps with an exit and re-entry after two, so don’t rush this too much.

The bike

The bike exits onto a fairly busy road. It’s brilliantly marshalled but stay alert. There’s a pedestrian crossing soon after, if you get a red relax and take in some calories. The 45km loop starts with the only flat section before tackling the first of many small climbs. The first real test is a short, steep climb after a left turn. Beware of clawing back time on the descent here; it’s on the narrow side, there are speed bumps and a sharp left at the bottom.

The other significant climb at 32km is 7km long but shallower, culminating in Pen-y-Pass. Again resist going flat out on the descent; stones, sheep, walkers and vehicles in the middle of the road are real dangers. When you start to struggle (and you will!) the stunning scenery can help ease the pain.

The run

The tame surfaces lull you into a false sense of security early on the run. At the end of Lake Padarn the road turns uphill and stays that way for 2km. Going too hard here’s a mistake. It’s then almost all downhill to the aid station. This contains some tricky rolling trails, tree roots and loose rocks.

Once the three laps are complete, medics check you/your backpack and you head up Wales’ tallest mountain. Before long, the tarmac kicks up at an horrendous angle.

This first Snowdon section is the hardest and, unless you’ve mountain running pedigree, power walking is your best bet.

Make sure you check-in with the medic before the summit and cautiously enjoy the return. All but the fastest few will finish in the dark, so a powerful head torch is strongly recommended.

For more information, check out the Brutal Triathlon event website.

Ironman Wales

Where: Tenby, Pembrokeshire, Wales
When: September

With bumper support and plenty of beauty, Ironman Wales is a classic on the Ironman circuit. But facing down IM Wales ain’t for the faint-hearted and we rated it the 9th toughest Iron in the world. Here are your ultimate tips from finisher and tri coach Mark Kleanthous.

Pre-race

In Tenby you have a 1km walk from transition to the swim start. If it’s cold and wet, wear your wetsuit to the start, otherwise put it on when you arrive. Allow enough time to get to the start and place your shoes and a drink in your allotted number spot on the zigzag stairs for the run to T1.

The swim

This is a scenic two-loop triangular swim. Keep left at the start to keep you out of the congestion during the rest of the swim. Use the giant rock that juts out in the bay, the lifeboat house, moored boats and the colourful houses overlooking the skyline to navigate.

But be careful running in soft sand after the first loop. Jog instead of running as you still have plenty of running to come. Remove your wetsuit after exiting the swim before the long 1km stretch to T1.

The bike

Hold back for the first 30mins of the bike and start hydrating after 5-10mins with water, and then start your nutrition plan. I’d use a road over a TT bike to combat the 18-22% steep hills.

The steepness of the climbs makes Tenby one of the hardest 180km courses, which requires you to have suitable gears to spin up and save your strength for the marathon. I’d recommend those wanting to complete the ride to use a 34/28t chainset. Those with sub 6:45hr ambitions go for a 34/26t or 42/32t.

There are a few technical sections, especially ‘Heartbreak Hill’ at Saundersfoot. Drive this section before and mentally plan how you’ll tackle it in both the dry and wet. Don’t get sucked in by the crowds; hold back and ride within your ability.

The run

The run course is demanding with the first 3km going straight uphill, which you have to complete four times. Because the hills are short and steep or long, the 42.2km demands that you keep mental control to hold back.

The downhills require you to relax and keep your shoulders loose to reduce impact. Far too many triathletes, including experienced Ironman competitors, push too hard on the early hills and are forced to slow up.

Success is only achieved by maintaining a constant effort. I’d wear a supportive run shoe to give you protection for the descents and cobbled parts.

We named Ironman Wales the 9th toughest Iron-distance triathlon in the world

For more information, check out the Ironman Wales event website.

Ironman Leeds

Where: Roundhay Park, Leeds

When: July

Taking place for the first time in 2025, Ironman Leeds becomes the UK’s fourth full-distance Ironman event. The playground of triathlon legends Jonny and Alistair Brownlee, Roundhay Park will be the epicenter of the course and the start location.

After an initial 3.8km lake swim, athletes will set off on a 180km loop exploring the rolling, Yorkshire Dales on two wheels. Not for the faint of heart, the bike route takes in a whopping 2500m elevation, and the hills don’t stop there.

The final marathon run leg will be several laps around the undulating 700-acre Roundhay Park. Made up of rolling parkland, woodland, and gardens, Roundhay is the UK’s largest urban park.

For more information, check out the Ironman Leeds event website.

The Northumbrian

Where: Kielder Forest, Northumbria, England
When: June

With a limited number of full-distance events now available in the UK, it’s nice to see new races coming into being, which is what happened a few years ago with the Northumbrian.

This is no easy feat (what full-distance race is?), with 3,606m of elevation across the two on-land legs and the run taking place on forest trails.

But the good news is that the course is stunning, with incredibly rugged views on hand to distract you as your legs ache and your lungs scream.

The bike leg also sees you go from England into Scotland, giving you the fun novelty of racing in two countries during one event.

For more information, check out The Northumbrian event website.

IronBourne Long Distance Triathlon

Where: Eastbourne
When: July

If you’re living in the south or south-east of England, here’s the long-distance triathlon for you. IronBourne takes place in Eastbourne and begins with a jump off the pier into the sea for the start of the swim leg.

The course is beginner-friendly and is also a fine option for anyone looking to break PBs. The bike leg is mostly undulating without any major climbs, but there are two ascents toward the end as you Friston and Beachy Head.

The run route is described as ‘fast and flat’ by the organisers, which will be music to the ears of many athletes.

For more information, check out the IronBourne event website.

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