In April 1815, and although the wars had ended with the [Treaty of Ghent]? in December of the previous year, many American prisoners of war still remained and some were unfortunate enough to be massacred in the prison at the behest of a British officer,who thought some were attempting to escape.
Dartmoor was reopened in 1851 as a civilian prison and has contained some of Britain's most serious offenders ever since. It has a (misplaced) reputation for being escape-proof.