Half ironman in the UK: 70.3 distances and races

A half ironman is a middle-distance triathlon: a 1.9 km swim, a 90 km bike and a 21.1 km run, or 1.2, 56 and 13.1 miles. Those miles add up to 70.3, which is where the IRONMAN 70.3 name comes from. In the UK, British Triathlon sets the minimum age at 18.

This guide explains the distances, the rules that apply to middle-distance races in the UK, and the UK races we could confirm on organisers' own pages, with 2027 dates where they have been published.

Half ironman distances

British Triathlon calls this format middle distance. Appendix A of the British Triathlon Competition Rules 2026 gives a "traditional" middle distance and a maximum for each leg.

The run is a half marathon. The bike is more than twice the 40 km ride of an Olympic triathlon and is the longest part of the day for most people. Because the rules give maximums, not fixed numbers, a race sold as middle distance can differ from 1.9, 90 and 21.1. The 2026 Swashbuckler, for example, used a 20 km run and added a 1 km run between the swim and transition. Always read the course page. For how middle distance fits with the other formats, see our guide to triathlon distances.

Half ironman, 70.3 or middle distance: what the names mean

• Middle distance is the British Triathlon term and the neutral one.
• Half ironman or half distance is how most athletes describe it, because it is half of a full-distance race.
• IRONMAN 70.3 is a branded race series owned by The IRONMAN Group. Only its own races use that name. In the UK they are in Bolton, Swansea and Weymouth.
• Other organisers run races over the same distances under their own names, such as the Outlaw Nottingham Half and the Outlaw Holkham Half.

The format is the same whichever name is on the entry page. The differences are in the venue, the course, the size of the field and the organiser's own rules.

Who can enter a middle-distance triathlon

Under British Triathlon rules the minimum age for middle distance is 18, counted as your age on 31 December of the race year. Long distance is 19. Organisers can set their own limits on top of this. The Outlaw Nottingham Half asks individual entrants to be 18 by 31 December 2027. Relay teams can include younger athletes on some legs: 17 for the swim and bike, 18 for the run.

It helps to race shorter distances first. Racing a standard (Olympic) triathlon gives you a sense of open-water swimming over 1500 m, pacing on the bike and running off the bike, all of which matter more over a longer day.

Rules that apply to half ironman races in the UK

Wetsuits

A middle-distance swim is longer than 1500 m, so it falls in British Triathlon's category for swims of 1501 m and above. For all ages, a wetsuit is mandatory below 15.9 °C and forbidden above 24.6 °C. Between those temperatures it is optional. This upper limit is higher than for sprint and standard races, where athletes aged 59 and under may not wear a wetsuit above 22 °C.

Cold water

Rule 4.4 sets limits when the water is cold. There is no open-water swim in competition below 11 °C. At 13 °C the swim is limited to 1000 m, at 12 °C to 600 m and at 11 °C to 300 m. The temperature is taken one hour before the start. Early-season races in lakes are the ones most likely to be affected.

Drafting

Under World Triathlon rules, age-group racing at middle distance is draft-illegal: you must not ride in another cyclist's slipstream. In British Triathlon rules the bike draft zone is 12 m long, measured from the leading edge of the front wheel of the rider ahead. You may enter it but must be seen to progress through it, with a maximum of 25 seconds to pass. Branded series can add their own race rules, so read the athlete guide for your race. Our guide to triathlon rules in the UK covers penalties, helmets and transition.

UK half ironman and middle-distance races

We list only details stated on the organisers' own pages, checked on 6 October 2026. The 2026 editions have already taken place. Where an organiser has not published a 2027 date, we say so.

IRONMAN 70.3 Bolton

The swim is at Pennington Flash Country Park and the run is in Bolton town centre and Queen's Park; the bike route is described on the official race page. The 2026 race took place on Sunday 7 June. Bolton Council reported more than 10,000 athletes across the race weekend, which also included a Night Run and IRONKIDS races. The 2027 date on ironman.com is 6 June.

IRONMAN 70.3 Swansea

The swim is in Prince of Wales Dock in Swansea. Ironman.com describes a 1.2 mile swim and a 56 mile bike. We could not confirm the 2026 date from an official page, so we do not give it. The 2027 date listed is 11 July.

IRONMAN 70.3 Weymouth

A sea swim in Weymouth Bay, Dorset, with the 1.2, 56 and 13.1 mile course described on ironman.com. The 2027 race is listed for 12 September. As with Swansea, we could not confirm the 2026 date from an official source.

Outlaw Nottingham Half

Run by Outlaw Triathlon at the National Water Sports Centre, Holme Pierrepont. The swim is in Regatta Lake with a time-trial start, which means athletes enter the water a few at a time. The 2027 race is on 23 May, as part of a weekend on 22 and 23 May that also includes a sprint, an aquabike (swim and bike only) and Future Outlaw races. Minimum ages are given above.

Outlaw Holkham Half

Outlaw's Holkham Weekend on 3 and 4 July 2027 includes a half, an aquabike, a gravel sprint, a 10K and Future Outlaw races. The organiser's home page lists the weekend. Check the event page for the swim venue and exact distances.

The Swashbuckler

Organised by Challenging Events Ltd and normally held at Buckler's Hard, Beaulieu, in the New Forest. In 2026 the organiser said a Buckler's Hard date was not possible because of limited high tides, so the race ran as "Swashbuckler On Tour" at Ellingham Water Ski Lake, Moyles Court School, near Ringwood, on Sunday 5 July 2026. The long course was a 1.9 km swim in two laps, a 1 km run to transition, a 90 km bike and a 20 km run. The 2027 date had not been published.

For the full calendar of UK races at all distances, see triathlon events in the UK.

Is there a full IRONMAN UK race?

Many people search for IRONMAN UK. When we checked ironman.com on 6 October 2026, we found no full-distance race of that name; the UK races listed were the three 70.3 events above. We also found no UK race from Challenge Family confirmed for 2027. The full-distance Outlaw in Nottingham lists 25 July 2027, with a 2.4 mile swim and a 112 mile bike, as part of its Original Weekend on 24 and 25 July.

Preparing for a half ironman

Training for middle distance takes months rather than weeks, and the long weekend ride is the core of most plans. A common structure is two or three sessions of each sport a week, with one long ride and one long run, plus regular brick sessions (a ride followed straight away by a run) to get used to running on tired legs. Our guide to the brick workout explains how to set one up. Keep most sessions easy and increase the load gradually.

Practise eating and drinking on the bike, and practise open-water swims of the full distance at a supervised venue. If you have a medical condition or have been inactive for a while, see your GP before you start. Training plans are general guidance and cannot promise a finishing time.

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