Dartmoor was one of a number of prisons used in late 19th and early 20th century to hold Irish prisoners in the War against England. A centre at Fron-Goch in Wales was also used for the same purpose in 1916 and it became known as "The University of Revolution" because it reurned so many prisoners who educated themselves inside and then returned to the War against England until Independence was won.
Equally, Dartmoor Prison was such as a 'University of Revolution" and major Irish leaders were held there.
In a way Prime Minister Blair's visit to Belfast today brings an end to that 800 year old conflict for, hopefully, all time.