All 2025 events now open for booking!

No. of days 1 day

Distance 10 - 50 km

Ascent gain 258 - 871 m

Accom. no

Food no

Set in the picture-perfect Chilterns, the Chiltern Challenge helps fund life-changing operations for children in developing countries and is the ideal 50km introduction to ultra marathon running. Escape to the Chilterns, an area of outstanding natural beauty. What's more, it's FREE to run, if you commit to raising funds for Humanity Direct.

There are now three options for this event: the full 50km ultra marathon, a 25km half ultra or a new 10km option!

NEW! For a limited time, enter all three 2025 Humanity Direct races for one great price!

Latest results

We are delighted to support SheRACES and commit to providing a great experience for female participants. Find out more

Included

  • Transport to and from Princes Risborough station
  • Free parking at Princes Risborough School
  • A fully recced and marked route
  • Full medical cover throughout
  • A quality finishers medal
  • Checkpoint food and water at regular intervals
  • Free tea, coffee and cake at the finish
  • Prizes and trophies for overall and category winners
  • A great atmosphere and a fun but challenging day out
  • Action photos en-route, free to download
The winners, runners up and age group winners will receive fantastic prizes or vouchers from our sponsors.

Route

The well-marked circular route will start and finish at Princes Risborough School. Using National Trails and Footpaths, there are clear signposts and post discs, as well as our signs and confidence tape.

We recommend you familiarise yourself with the route before the start of the race and download the GPX file or OS Maps route onto your watch or phone.

Download printable route information.

Showing route for:

Checkpoints

#1 Village Green, Dunsmore HP22 6QJ ///rescue.emphasis.overture Grid ref: SP86210521

#2 J/W Ridgeway, Gadmore Lane & Shire Lane, Hastoe HP23 6LU ///riper.divorcing.served Grid ref: SP91390920

#3 Asheridge Farm, Ashotts Lane HP5 2UU ///laptop.pull.billiard Grid ref: SP93000537

#4 Cobblershill Farm, Cobblershill Lane HP16 9PW ///delusions.courts.diverting Grid ref: SP86940365

More info...

Toilets

CP1, Dunsmore Village Hall HP22 6QJ ///sailor.countries.bench

Great Missenden, Bough's Meadow Link RD HP16 9AL ///boggles.smarting.diets

Checkpoints

#1 Village Green, Dunsmore HP22 6QJ ///rescue.emphasis.overture Grid ref: SP86210521

#2 Cobblershill Farm, Cobblershill Lane HP16 9PW ///delusions.courts.diverting Grid ref: SP86940365

More info...

Toilets

CP1, Dunsmore Village Hall HP22 6QJ ///sailor.countries.bench

Schedule

07:00

Minibus pick up starts from Princes Risborough Station

07:15

Registration opens

08:00

Walkers mass start

08:30

Walker/runners mass start

09:00

Runners mass start

10:00

25km mass start

10:30

10km mass start

14:00

Refreshments available

14:00

Minibus to the station running all afternoon

16:00

Prize giving or when enough runners have finished

Pricing

Fundraise

FREE

10km - Standard entry

£35

Ultra - Early bird entry

£62

Half ultra - Early bird entry

£36

Ultra - Standard entry

£69

Half ultra - Standard entry

£42

Ultra - Late entry

£75

Half ultra - Late entry

£46

The entry fee will be donated to fund a vital operation, or alternatively enter for FREE, if you commit to raise funds for Humanity Direct.

If you're fundraising book now through our system, then visit Humanity Direct's website to register yourself.

Please note: a 2.5% service charge, levied by the registration software, will be added to your total. We are using a new entry system that takes payment through the secure system Stripe. No payment information is retained by Extreme Energy, or our entry system tool.

Email us on info@xnrg.co.uk if you have any questions about your options.

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If for some reason you are not able to make the event you have entered. The XNRG refund policy is that we will give you 70% refund of your entry fee up to 1 month before the start date of the event. You also have the option (1 month before the date of the event) to get a 100% transfer credit to another one of the other Humanity Direct 1 day events, or you can donate your entry fee to the charity. All entry fee money goes directly to the charity and directly to helping children with life changing operations. These options you can execute on your Ultrabritain entry page.

After this time we are sorry there will be no refunds or transfers to future events. Refunds will be to your booking credit card.

Race-day Preparation

Kit List

The only compulsory kit is a fully charged mobile phone and a minimum 500ml of water, but it's worth taking a look at our recommended kit list.

Other equipment may be made compulsory by the race director depending on the weather.

Medical

The event is supported by a Course Manager and a fully qualified medical crew will be in attendance. We strongly recommend taking a moment to read our medical page before booking.

FAQ

We've answered a range of common questions in our FAQ. For other questions, say hello on info@xnrg.co.uk.

Registration

Please register and pick up your timing chip from:

More Information

This popular race is especially good for those looking for a supportive event for their first ultra within easy reach of London. And for those wishing to build experience to gain entry to UTMB we can now also offer 2 ITRA points (for full ultra distance only)!

As with all of our events, everything is taken care of at the Chiltern Challenge so you can focus on the experience! We’ll provide transfers from the station, free parking, free photos, changing facilities and heaps of tea and cake.

The XNRG Chiltern Challenge is a unique chance to get a place on an amazing one day ultra for FREE if you fundraise for a Humanity Direct patient, or alternatively your entry fee will be donated in full to Humanity Direct. Do something amazing and have a great day out with us!

So, how does it work?

It's simple. The entry fee is donated to fund a vital operation or, if you prefer, you can enter for FREE and start a fundraising page instead and raise as much as you can, with a minimum of £69.

100% of donations go towards children's operations and medical care in developing countries through Humanity Direct.

Why We Do It

Since teaming up with Humanity Direct in 2016, our Humanity Direct races have helped to raise over £150,000, funding hundreds of life saving and life changing operations for children who either can't afford, or can't reach, the surgery they need.

“The support we’ve had from XNRG has been phenomenal. Thanks to you we’ve rolled out a vital eye-testing programme for children in rural Uganda with over 600 children receiving free glasses so far. Your donations and dedication have also helped us continue to provide life-saving and life-changing surgery for children whose families are live on less than a $1 a day and who would never be able to afford the medical care they need.  XNRG ultras truly do change lives!"

- Nick Swift, Humanity Direct’s Founder

Entries

Entries will close one week before the event (or when full). A waitlist option will be available if the event becomes fully booked.

Navigation and Support

Stretching from the River Thames in Oxfordshire to Hitchin in Hertfordshire, the Chiltern Hills are a spectacular Area of Natural Beauty boasting some of the finest protected countryside in the UK.

The well-marked circular route will start and finish at Princes Risborough School (HP27 0DR), incorporating four checkpoints for the full ultra distance, approximately 10km apart, and two at the half ultra. (There won't be any checkpoints on the 10km route.)

Using National Trails and Footpaths, there are clear signposts and post discs, as well as our signs and confidence tape. We recommend you familiarise yourself with the route before the start of the race and download the GPX file or OS Maps route onto your watch or phone.

Aid stations

There will be checkpoints at regular intervals with water and food - please bring your own cups. For the full ultra distance there will be four checkpoints and the half ultra will have two. (Please note: there will not be any checkpoints on the 10km route.)

Due to the risk of cross contamination, we cannot provide checkpoint food to suit all dietary requirements. If you require special food or snacks to suit any allergies or vegetarian/vegan diets, can you please bring your own. Put them in containers, marked with your name and checkpoint number and give them to the checkpoint teams at the start of the race.

Trees Not Tees

Event T-shirts are no longer included in the cost. The cost of T-shirts goes to Trees not Tees and a tree will be planted instead. You have the option of purchasing a T-shirt when entering the event, if you'd like one. T-shirts are available to order until 2 weeks before the race.

For more details visit their website - https://treesnottees.com/

Reviews

Hi, I don't usually respond to organisers after an event. I just wanted to say thanks for organising such an amazing first ultra. The race was superbly organised , well planned , Marshall ands food stops were excellent. I can assure you I will be running in your events again and recommend them to others. Thank you and your team for making the chilterns ultra such a great run.

Hi everybody I would like to congratulate XNRG on a superbly well run event in the Chilterns. It was a fabulous day out in stunning countryside. Everything went like clockwork, registration, briefing and the course was marked perfectly with tape, signs and sometimes quite elaborate pictograms sprayed on the ground making the maps supplied only necessary as an overview of the route. I find it quite mind boggling that you can plot and mark such a varied and interesting course in 31 miles of countryside, check it and then clear up afterwards. It made the entry fee worth it alone.

Just wanted to say thank you to everyone who helped with this event yesterday. It was my first ultra and I absolutely loved it! The fantastic organisation meant all I had to do was concentrate on getting myself round the distance! The malt loaf and coke at the checkpoints were a much needed treat! Thanks again.

We can't wait to see you there! Questions? Say hello on info@xnrg.co.uk

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