Deepest underground marathon distance run (team)

The deepest underground marathon distance run (team) is 1041.1m (3416ft 11in) and was achieved by Army Cadets (UK) at ICL-Boulby, Middlesbrough, UK, on 10 October 2020.

Seven runners commenced the attempt having to run in an underground mine tunnel at a measured measured distance of 5.54Km. They had to run this length 7 times then a final measured length of 3.72Km giving a total distance of 42.5Km. This meant they would run 0.305Km further than the recognised marathon distance. One runner had to stop at the half-marathon mark so only six runners completed the distance - the minimum requirements being two runners.