HM Prison, Dartmoor

The prison at Princetown was originally built by French prisoners of war during the Napoleonic Wars. In Bulldog Five, Captain Varkerly's wife - Ruth - ends up seeking sanctuary in the closed prison, leading a small group of survivors while pregnant with Varkerly's first child.

Dartmoor Prison at Princetown including the transmitter behind the prison mentioned in Bulldog Five

The sign to Princetown can be confusing as it has the Cornish shield above the writing, despite being located in Devon. A lesser known fact is the Prison and much of the land is the property of the Duchy of Cornwall whose estates consist of many such locations outside of Cornwall