Bath 200-mile ultra-marathon in railway tunnel begins
A 200-mile-long (322km) ultra-marathon through a dark, unused railway tunnel begins on Friday.
The ultra-mararthon takes place in Combe Down tunnel in Bath, which is the longest foot tunnel in the UK.
Participants of the event must repeatedly run out and back on the one-mile stretch of underground road within 55 hours to complete the challenge.
The challenge is described as a "mind-bending test of extreme endurance and sensory deprivation".
In the past, the gruelling experience has left participants hallucinating.
To qualify, runners must have a previous 100-mile (160km) race result.
Anybody that fails to reach 100 miles (160km) by 27 hours and 30 minutes is timed out of the ultra-marathon.
Andy Persson is a counsellor who offers walk-and-talk counselling sessions around the Downs in neighbouring Bristol.
He did not start running until his mid 40s, and gradually challenged himself to cover longer distances until he was ready to take part in the ultra-marathon in 2020.
It took him 53 hours to finish and he described the experience as "a bit of a rollercoaster ride".
"Within long distance endurance things, you always go through these ups and downs and it's quite representative of life.
"If you keep pushing through those difficult, dark times, you get through it and suddenly everything feels great again", he said.
The ultramarathon challenge ends on 2 April.
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