The Tunnel

This challenge is a 200 mile ultramarathon through the darkness of the UK'S longest foot tunnel. You will run on flat terrain but in the pitch black between 11pm and 5am, there will be low level lighting in effect at other times. The Combe Down tunnel is in Bath, Somerset and there will be a checkckpoint at the south end of the tunnel. You will have 55 hours to run approximately 100 'out-n-backs', or 200 times through the tunnel, which is possibly the greatest mileage ultramarathon ever run 99% underground. The Tunnel is sponsored by Chia Charge.