Mountain Mayhem is a massive 24 hour enduro event. Last year there were 2,650 competitors and over 15,000 spectators.
The event is held at Eastnor Catle Deer Park near Ledbury in Herefordshire. Google map of location.
As well as the enduro mountain bike event there’s also the Midsummer Madness run round the course, K9 running (trail dog + runner), the Sunday Munch road ride and the obligatory “much, much more”.