United Kingdom · England
Distance
161 km
Date
Entry fee
£220
€ / km
€1.57
Autumn 100 (A100): England's Flattest 100-Mile Trail Race, Measured
Autumn 100 (A100) is a 100-mile trail race held by Centurion Running on October 17–18, 2026, starting at 9:00 AM from Goring-on-Thames in Oxfordshire, England. The course covers 161 km with 1,500 m of gain (9.3 m/km) — placing it in the top 5% flattest measured courses in the DTR database at rank 372 of 383 by elevation density. The format is four 25-mile out-and-back spurs, all returning to Goring Village Hall race HQ, alternating between the flat Thames Path river sections and the hillier Ridgeway ancient trackway. 69.8% of the course is flat terrain; the average uphill gradient of 4.6% is the 371st gentlest of 390 measured courses in the database — virtually every climb is runnable.
The men's course record is 13:58 (Geoff Cheshire). Entry costs £1.57/km (£220 UKA affiliated). London Heathrow (LHR) is 52 minutes away by road, with good train connections to Goring. Founded in 2012 and organised by Centurion Running — the UK's most established 100-mile series — the A100 has 170–175 finishers in recent editions. Entry requires a sub-15hr 50-mile finish since January 2021. It suits runners targeting their first 100-mile finish or a fast-course 100-mile benchmark, particularly those coming from road or flatter trail backgrounds.
Elevation and Terrain
Total Meters
1,500m
D+/KM
9.3m/km
For context, the Tor des Géants 330 loop has 73 D+/km.
Avg Uphill Gradient
4.6%
Avg Downhill Gradient
-4.6%
Uphill gradient distribution
| 2–5% | 17.0 km | |
|---|---|---|
| 5–10% | 5.8 km | |
| 10–15% | 0.8 km | |
| 15–20% | 0.2 km | |
| 20%+ | 0.2 km |
Route Profile
AnalysedTerrain breakdown
| 15.0% | Uphill |
|---|---|
| 69.8% | Flat |
| 15.2% | Downhill |
Terrain
Autumn 100 – 161 km 161km Top Climbs
Top Climbs
| 1 | 3.9 km · 130 m gain starts km 53 · avg 3.4% · max 18.3% |
|---|---|
| 2 | 1.8 km · 88 m gain starts km 84 · avg 4.9% · max 9.7% |
| 3 | 1.0 km · 59 m gain starts km 61 · avg 6.2% · max 25.6% |
Top descents
| 1 | 3.8 km · 130 m drop starts km 64 · avg -3.4% · max -18.2% |
|---|---|
| 2 | 2.1 km · 91 m drop starts km 115 · avg -4.3% · max -9.2% |
| 3 | 1.0 km · 59 m drop starts km 59 · avg -6.0% · max -25.3% |
How Flat Is the Autumn 100?
How Flat Is the Autumn 100?▼
Extremely flat. The Autumn 100 covers 161km with approximately 1,500m of total gain, 9.3m per kilometre, ranking 372nd of 383 measured courses in the DTR database by elevation density. Only 11 courses in the database have less gain per km.
Autumn 100 Course Format
What is the Autumn 100 course format?▼
Four 25-mile out-and-back spurs, all starting and finishing at Goring Village Hall race HQ in Oxfordshire. Legs 1 and 4 follow the Thames Path (flat, riverside). Legs 2 and 3 climb onto the Ridgeway National Trail (hillier, ancient woodland). The format means crews can support at HQ after each 25-mile leg — four access points across the race.
£1.57/km for a Centurion 100-Miler: Is the Autumn 100 Good Value?
£1.57/km for a Centurion 100-Miler: Is the Autumn 100 Good Value?▼
£220 for UKA-affiliated runners (£222 unaffiliated), £1.57 per kilometre for a professionally organised 100-mile race with 16 aid stations, full medical support, and course markings throughout, a price falling in the middle of our cost per km rankings.
Travel Guide for Autumn 100 - Airport, Race Transfers, and Accomodations
Why London Heathrow Airport (LHR) is the best choice for Autumn 100?
▼
London Heathrow LHR is only 52 minutes to start point(Goring Village). Good train connections: London → Goring and Streatley. Goring and Streatley offers variety of local accommodation options which is situated within walking distance of the start/finish line of the race
Autumn 100 – 161 km 161km GPX
Getting to Autumn 100 – 161 km
Nearest airport
London Heathrow (LHR)
Notes
Start: ~1–1.5 hrs / Public transport: Good (train to Goring and Streatley) / Accommodation: Easy (Oxford/Reading area)
