Green Mile Day Marathon 2026

The Green Mile Day Marathon is run inside the former HMP Dorchester in Dorchester, Dorset, England, with the start listed at postcode DT1 1JD. The main race is a full marathon of 42.195 km, and the event also offers an 83 km road race and a night option. The prison setting is the point: the marathon stays completely inside the prison, which the organisers describe as the only marathon in the world run entirely within one. Runners can tackle gruelling stairs in daylight, in the dark, or both, and the programme includes a spooky Halloween evening edition for anyone who wants the prison atmosphere turned up another notch.