Thames Path 100: London to Oxford's Flattest 100-Mile Ultra, Measured

The Thames Path 100 (TP100) is a 100-mile (161km) continuous trail race from Richmond in South West London to Oxford, following the Thames Path National Trail. Organised by Centurion Running since 2012, it is now in its 15th edition. The course gains approximately 1,900 feet (around 579m) of elevation — extremely low for a race of this length — with 75 percent trail or gravel and 25 percent paved tow-path. The race starts at Richmond New Waterfront at 09:00 and finishes at Queen's College Sports Ground, Oxford, with a 30-hour cut-off. The TP100 is one of the flattest 100-mile ultras in Europe and ranks 4th flattest overall in the DiscoverTrailRaces database of nearly 390 measured trail races.

The Thames Path 100 is exceptionally flat by every measured metric. It ranks 4th flattest out of approximately 390 trail races in the DiscoverTrailRaces database by proportion of flat terrain, and 5th-lowest for elevation gain per kilometre at roughly 11.8 m/km. The average uphill gradient across all climbing sections is around 3.95 percent — the 8th gentlest in the database — and the average descent gradient ranks 7th gentlest of all measured courses (inverted scale where rank 1 equals most gentle). This makes the TP100 significant in two ways: it is genuinely accessible for runners who struggle with technical mountain terrain, and it creates a unique mental challenge — 161 kilometres of flat, featureless riverside running tests pacing discipline and mental resilience far more than gradient management.

Entry costs £220 for affiliated runners (£222 unaffiliated). The 2026 edition was sold out and running on a waitlist, with 300 places available. Entries typically open by ballot and fill very quickly. A qualifying race is required: runners must have completed a 50-mile event within 15 hours between 1 January 2020 and race day. The race is part of Centurion Running's Grand Slam of four 100-mile races; Grand Slam entries open alongside individual race entries. The 2026 date was 2 May; 2027 entry details are expected to be announced later in 2026.

Yes. The Thames Path 100 is a qualifying race for the Western States Endurance Run (WSER), the most prestigious 100-mile trail race in the world, held annually in California. To use the TP100 as a WSER qualifier, runners must finish the race within the cut-off time (30 hours) in the year of their WSER application. Runners still enter the WSER lottery separately — completing a qualifier gives one lottery ticket, with additional tickets for each subsequent year of unsuccessful applications. The TP100 also has UTMB Running Stones (7.02 stones awarded on completion). WSER qualification applies to finishers of the full 161km distance only.

The race starts at Richmond New Waterfront in Richmond, South West London. Richmond is served by London Overground and District Line Underground services (Richmond station), approximately 30 minutes from central London. The nearest major airport is London Heathrow (LHR), roughly 22 minutes by road; London Gatwick (LGW) is also accessible. The race finishes at Queen's College Sports Ground in Oxford. Oxford is served by direct trains from London Paddington (approximately 55 minutes), making the point-to-point logistics manageable without a car — runners can take the train or a pre-arranged coach back to London after finishing.