The lone cavalier that tried to flee from Cromwells men, made it as far as this arch you see here.
The arch itself was built as part of a Norman monastery in 1170 and was in continual use up to 1535, around the time of the dissolution of the monasteries. By 1646, during the civil war, it had long fallen out of use, by this point just a shell. The cavalier fleeing Cromwell’s men may well have thought it the perfect place to hide in his hour of need. Unfortunately, it offered him no sanctuary and he was brutally murdered by Cromwell's men.
Local legend has it on moonlit nights you can see a shadowy figure and it’s even been reported that dogs refuse to walk through the arch itself. Barking and whining at some unseen person blocking their path!

Sources:
www.solosophie.com/cromwells-arch-bovey-tracey-history/
dartmoorpreservation.co.uk/the-ghostly-cavaliers-of-dartmoor/