11/03/2026
The Thames Ring Series is one of the most brutal endurance challenges in British ultrarunning. The headline event is the TR250, a roughly 250 to 256 mile loop starting and finishing in Streatley on Thames. The course follows the River Thames east, then heads north along the Grand Union Canal before returning via the Oxford Canal, almost entirely on canal towpaths and riverside paths. Runners must navigate the route themselves and have just 100 hours to complete the full distance, moving day and night with checkpoints roughly every 25 miles.
In 2026 the event is expanding into a full series, adding two shorter but still formidable options. The TR150 covers around 150 miles from the start to Nether Heyford with a 53 hour cutoff, while the TR100 runs the final 100 mile section back to Streatley with 34 hours to finish. All three races demand careful pacing, resilience through sleepless nights, and the ability to keep moving long after most people would stop.
To understand the scale of the challenge, consider this. Only 164 people have ever finished the full Thames Ring 250. More humans have travelled to the International Space Station, around 290 in total. In the last two years alone, 166 runners have finished the Winter Spine Race, with 78 in 2025 and 88 in 2026.
Finishing the Thames Ring is rarer than reaching orbit and remains one of the most quietly formidable achievements in endurance running.
Entries for 2026 and 2027 open.
https://www.challenge-running.com/e/thames-ring-series-11289
