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XNRG 2021 events now open for booking!

No. of days 1 day

Distance 16 mi

Ascent gain 648 m

Accom. no

Food no

Extreme Energy is delighted to announce a one day 25 km challenges. These events are open to walkers and runners, young and old, experienced or in-experienced. Our objective is to create a 25km “intro” Half Ultra Distance Event. We have made everything easy for our competitors on a scenic trail route, which is easily accessible by road and rail. It is fully marked and very well supported en-route. Why an “intro” half ultra? Whilst the experienced competitor will enjoy taking part in these events, we wanted to attract more people into the great world of ultra running by putting on an all encompassing one day event. The Chilterns are a stunning part of the country side and the route, whilst hilly in places, has great views and a mixture of terrain.

Latest results


  • Transport to and from Princes Risborough station
  • Free parking at Princes Risborough School
  • A fully recced and marked route to make the event special and challenging for all
  • Full medical cover throughout
  • A quality finishers Technical T Shirt.
  • Quality finishers medal
  • Toilets/showers and changing facilities
  • Checkpoint food and water throughout
  • Free tea, coffee and cake at the finish
  • Prizes and trophies for overall winners.
  • A great atmosphere and a fun, but challenging day out
  • Action photos en-route, free to download


The "Chiltern 25Km Challenge" is run on National Trails and Footpaths and has some excellent markings in the form of signposts or post discs. However, since it's made up of sections of these trails and paths the route will be comprehensively marked with signs and confidence tape. In addition, you will be given a map, which is designed to help on any tricky sections, to provide information on any route changes and to indicate where the checkpoints are.



Minibus pick up starts from Princes Risborough Station


Registration open


Walkers briefing


Walkers Start


Runners race briefing


Runners Start


Elite runners briefing (target time below 6 hours)


Elite runners start


Massage and refreshments available


Minibus to the station running all afternoon


Prize giving or when enough winners have finished


Standard entry


until 31st May 2015

Late entry


from 1st June 2015

Please note: A 3% service charge, levied by the registration software, will be added to your final amount.

No refunds or deferrals will be made within one month of the event start.

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.


The event is supported by our course manager and his experienced on-course crew to ensure you have a great event. A fully qualified medical crew will also be there to give first aid and manage any serious medical problems in cooperation with the emergency services. We strongly recommend taking a moment to read our medical page before booking.


We've answered a range of common questions in our FAQ. For other questions, say hello on

Download race details

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