Originally conceived as a impregnable defence against the French after the loss of Normandy in 1204, Mont Orgueil Castle was also a symbol of power perched on its lofty promontory which was easily visible from the French coast. However, as gunpowder and cannon replaced sword, bow and arrow, the Castle became vulnerable from ship cannon, as well as cannon sited on the adjacent hill, Mont St Nicolas.

Successive modifications designed to counter cannon fire were made culminating in the construction of the Grand Battery and Somerset Keep facing inland towards Mont St Nicholas in the mid to late-16th century. With the quickening advancement of cannon technology, the Tudor artillery fortress was never fully completed as designed by the military engineers of the time, and quickly fell out of use, being replaced by the newly built Elizabeth Castle.