Chiltern Hills 100K
Race details
Next edition - 9th May 2026
A 100K ultra marathon along the best and most loved trails within the Chiltern Hills.
The Chiltern Hills 100K will return on May 9th, 2026 - Entries will open on 10th May.
The route starts and finishes in Chesham with runners completing an anticlockwise loop passing many landmarks along the way, including Ashridge Esate, Coombe Hill & Bledlow Ridge and incorporating sections along The Ridgeway, Chiltern Way and South Bucks Way.
100K Ultra (first 25 entries)
£142/140 (UKA Affiliated)
100K Ultra
£152/150 (UKA Affiliated)
Key Information
Race held under UKA rules.
Event Downloads
Last updated - Feb 2025: Updated route files with confirmed CP6 location
Route Map
Route Description
The route starts in Chesham and follows an anticlockwise loop along some of our favorite trails in the Chilterns.
The first leg to CP1 (14K) follows the Chiltern Link trail and heads east to Hastoe. From this first checkpoint, runners complete a loop around National Trust's Ashridge Estate, via Little Gaddesden (CP2), which includes a stunning section of The Ridgeway from Ivinghoe Beacon to Aldbury.
Once back at Hastoe (CP3 - 41.4k), runners will have access to their drop bag before continuing along The Ridgeway, passing through Tring Park, Wendover, Coombe Hill, Whiteleaf Hill (CP4 - 57.8K), and along to Bledlow Ridge.
The Bledlow Ridge Village Hall checkpoint marks 75K into the race; the final leg follows a selection of woodland trails through Hampden and along to Great Missenden.
From Missenden, the end is in sight as the loop is complete, and you arrive back in Chesham.
Keep scrolling for more event info
Aid stations
There are six checkpoints on the route. All checkpoints will contain the following items.
- Water
- Coke
- Precision Fuel & Hydration - PH 1000 Electrolyte Drink (pre-mixed)
- Precision Fuel & Hydration - PF 30 Gels
- Precision Fuel & Hydration - PF 30 Chews
- Selection of crisps and sweets
- Pre-made sandwiches (jam, peanut butter, cheese)
- Chia Charge Mini Flapjacks
- Selection of Fresh fruit (banana, orange, watermelon)
- Hot drinks/water available 44k, 60k & 75k
Event base
The event is hosted at Chesham Guides Headquarters, based in Lowndes Park in Chesham.
The guide hut has direct access to the trail and is an ideal location for the start/finish.
Post-race food will be available to all runners.
Required gear
All runners will be required to carry the following items for the entirety of the run:
- Mobile phone (emergency number saved)
- Route GPX on watch/phone
- Refillable water/hydration system (0.5L min)
- Waterproof or windproof jacket
- Additional long sleeve layer (to be kept dry for emergencies)
- Additional full leg cover (to be kept dry for emergencies)
- Head torch + spare battery
- Warm hat/buff & gloves
- Reusable cup
- Basic first aid supplies (plasters/tape/bandage/foil blanket)
- Bag/vest/belt to put everything in
- £20 cash or bank card
- Race nutrition
Entry details
Registration is £152 (or £150 to affiliated runners). The first 25 runners will recieve a £10 discount. Runners must be aged 20 years or older.
- Entry to the 100K race
- Event permitted by the TRA/UKA
- Finishers medal
- GPS Tracking
- Chip timing with live results
- Medical support
- Marked/marshalled route
- Drop bag at Hastoe CP.
- Event photos
- Post race meal
Withdrawal options
By entering our race, you agree to the following withdrawal policy. This policy applies to all runners with the exception of women of cannot compete due to pregnancy.
*Entrants to The Ridgeway Challenge are entitled to defer their entry for up to 2 years, or receive a 90% entry voucher to use on any Runaway Racing event.
Credits can be used on future race entries, any time during the following 2 years.
Withdrawal requests must be completed online via our manage booking functionality.
Manage Booking
It was so well organised both in the weeks building up to it and on the day, and the course was so well marked you couldn’t possibly go wrong out there.
Darren
Chiltern Ridge 50km, 2021
Loved this! Course was beautiful and very well signposted. Friendly and really helpful marshals. Aid stations well stocked. Very well organised- would definitely do again.
Dee
Chiltern Ridge 50km, 2023
