Near the end of the war it was renamed Special Camp XI and used to detain many senior SS military leaders who were awaiting extradition to the Nuremberg trials.
The prefabricated concrete huts surrounded by open fields at Island Farm were considered ideal, although the barracks had to be converted and barbed wire fences erected.
Some of the techniques used by the inmates were ingenious and resembled those shown in the (postwar) war film The Great Escape about Allied POWs.
To support the tunnel roof, oak benches were stolen from the canteen and bed legs were cut down when supplies of wood were depleted.
At around 10pm on March 10, the prisoners made their move; a few stole the local doctor's car and got as far as Birmingham, at least 120 miles (190 km) away, and another group got to the port of Southampton.
The prisoners knew their way around through crude but accurate drawings of Wales and the surrounding area, mainly of railway lines and principal roads.
It was then designated Special Camp Eleven and was prepared to receive senior German officers, many of whom had been captured in France and were awaiting trial at Nuremberg.
In all there were 160 officers holding the rank of general, admiral, or field marshal, including a number of Hitler's closest advisers: Island Farm Camp finally closed in 1948, when the last prisoners were returned to Germany.