Full Iron Distance "The Bastion" set to take place at Château de Chantilly on June 8 2025 !

Introducing the Bastion

Named “the Bastion”, this ultra triathlon will test even the most hardy athletes. The Bastion features a 3.8km swim, a true toughie of a 180km bike course and a stunning 42.2km run course that takes place through the grounds of the beautiful château.

A “bastion” is a stronghold, a place soldiers regroup and prepare for the next round of fighting. That resilience and desire to fight on is most definitely what will be required to conquer this life defining endurance race. This full iron distance race will test even the most courageous warrior!


  • Swim (at point of swim exit):
    2 hours 20 minutes (+10 minutes for transition 1)
  • Cycle:
    9 hours and 45 minutes (allows average speed of 24km/h)
  • Swim, transition 1, cycle and transition 2 (at T2 exit point):
    10 hours (from start of race)
  • Overall cut-off (must have started last lap of run):
    14 hours 30 minutes (from start of race).
  • If competitor has not completed third run lap by 21:30,  they will not be able to continue and will be directed down the finish chute instead

Majestic race at the château

Château de Chantilly’s majestic grounds and the surrounding areas are the perfect setting for this fast, flat full iron distance triathlon. Finishing this immense challenge in front of the beautiful château will be a high point on any triathletes list of ‘must do’ races.

The Bastion 140.6 will be part of a wider festival of multisport at the château over the weekend of 7-8 June, coinciding with 2025 hosting our 15th edition of the event.

The château is a short train ride from Paris and is perfectly located to be accessible to athletes from the whole of France and beyond.


Competitor provisions

Each Bastion entrant will receive a finisher t-shirt, rucksack, a post-race meal, massage along with our iconic medal. The Bastion will provide affordable racing at the full iron distance with professional, specialist assistance throughout the race.

From booking right through until after your race we are here to support you as an athlete and can provide advice and tips in your training, nutrition, kit in the lead up to your race.

We will be here to give you a full in depth briefing both online and in person, which will cover important safety and course details to ensure you are fully confident on race day. Our aim is for you to have the best race day from start claxon to finish line.

our wealth of experience

We look forward to welcoming athletes for this immense feat on 8 June 2025. We’re thrilled that we are able to host such an iconic race in such a magnificent venue.

Our wealth of experience hosting full iron distance endurance events having hosted them for over 10 years across the Channel in the UK will ensure a well run and highly organised event leaving you to focus on one thing: your race.


Our booking form is now open! Set yourself this mighty challenge for 2025 and get ahead with your training. Book early to secure the biggest discount:

  • first 50 entries will receive the discounted price of €300
  • next 50 entries will receive the discounted price of €350
  • further entries will be at the non discounted price of €400


Learn more