The main town of Jersey is named after a Belgian monk called Helier.  He set up home in a cave on the high rock, which was later incorporated into the chapel, built in the 12th century, which now bear the names Hermitage Rock and Hermitage Chapel. Helier was killed by marauding pirates from Normandy in AD555 and later made a saint

The earliest known structure to be built on the two rocky outcrops on which the Castle was subsequently to be built was the Priory of St Helier, thought to have been founded as a monastery and oratory in 1155 but amalgamated with the Abbey of Cherbourg and downgraded to a priory in 1179.

The remaining buildings of the Priory were enclosed by the defences of the Lower Ward of Elizabeth Castle, constructed between 1626 and 1636. The church tower is said to have been demolished in 1639 and the nave was in use as a chapel in 1646.

Royalist forces held the Castle during the English Civil War when a mortar shell fired by Parliamentarian forces in St Helier crashed through the Priory roof, exploding 12 barrels of gunpowder stored there, badly damaging the building.

The buildings appear in several drawings prepared in 1650 and 1651 and – what remained of them – were included on Thomas Phillips’ plan of the Castle prepared in 1680, by which time they were used as a chapel, stables and a cistern. It is not known precisely when the last traces of the walls of the Priory were finally demolished but this must have occurred before the Officers’ Quarters were built partially on the site of the Priory Church in 1735.

The first attempts to construct defences on the islet where Elizabeth Castle stands, were in 1550 and 1551, when orders were issued to build a gun battery to be garrisoned by six gunners. It is not clear, however, whether these works were ever undertaken or completed.

By the 16th century, cannon and gunpowder had become the dominant weapon of war. By the end of the century the principal castle on Jersey, Mont Orgueil, was out of date and vulnerable to bombardment from Mont St Nicholas. A new site was chosen on the small islet in St Aubin’s Bay and a new castle was built. Sir Walter Raleigh, who was Governor of Jersey between 1600 and 1603, chose the name Elizabeth Castle, after Queen Elizabeth I, and the name has been retained ever since.

Elizabeth Castle remained in use up to and including the Second World War, when it was occupied by the Nazis. The occupation by the German forces commenced on 1st July 1940 and eventually ended on 9th May 1945 – Liberation Day. However, Elizabeth Castle was not handed back to the Island by the military until 19th May 1946. During this period the island was heavily fortified using Organisation Todt construction workers from various parts of Europe, including Russia and Spain.

A concrete fire-control tower was built in the Upper Keep, with an anti-aircraft position on the roof, whilst two anti-aircraft guns were mounted on the existing emplacements in the Lower Keep and a searchlight platform was built in Raleigh’s Yard.

A series of huge concrete bomb shelters and gun emplacements were added to the Castle, with many of them surviving to the present day.