The Tunnel Marathon
Below are the key details about the running event along with a Google map & search link. Spot any mistakes or missing info? Use the 'Report' button below.
- When
- 21 Nov 2026
- Distances
- Marathon
- Location
- Cosham, Hampshire
- Terrain
- Trail
- Event website
- http://www.sussextrailevents.com/
About The Tunnel Marathon
The Tunnel Marathon takes runners underground for a full 26.2-mile trail marathon through a former Royal Navy headquarters near Portsmouth. The route uses several tunnels within UCAP Bunker, a Cold War-era facility located 100 feet below ground and originally used as an underground HQ during the planning of the D-Day invasion. Some tunnel sections are only 6 feet tall, requiring runners to stoop through roughly 20-metre stretches—a consideration for taller participants, particularly as these sections are repeated throughout the lapped course.
Taking place on 21 November 2026, this is the third edition of the UK's first fully underground marathon. The event operates under ARC Running Club rules, with permit and insurance details available at the start.
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