Fort Blockhouse is a
military establishment in
Gosport,
Hampshire,
England, and the final version of a complicated site. It is surrounded on three sides by water and provides the best view of the entrance to
Portsmouth Harbour. It is unique in two respects - firstly, it was built over a number of centuries. Secondly, it is thought to be the oldest fortified position in the
United Kingdom that is still in active military use.