Mont Orgueil castle

As long as the Channel Islands were part of Normandy there was no need to build a major fortress here. The situation changed in the early 1200s when King Philippe Augustus of France invaded Normandy and the islands became a frontier post on the edge of a war-zone.

King John of England who was also the Duke of Normandy recognised that the Channel Islands were strategically important. They were a useful toe-hold in the region from which to re-establish his authority in Normandy. This meant that French troops who could otherwise be used in the Aquitaine border areas or threatening England had to be kept in the region.

The harbour in St.Peter Port, Guernsey was also a useful staging point to gather the wine convoy before starting on the most dangerous leg of the journey from Bordeaux to Southampton.

The Channel Islands' harbours provided a southern base from which English ships could patrol the English Channel.

With all this in mind, he ordered money to be raised for the defence of the islands. The main fortress in the islands was built at Mont Orgueil in Jersey because of its prime position.

The castle was built on a promontory so that the sea and cliffs protected it on three sides.

The granite outcrop, provided it with firm foundations so it was virtually impossible to undermine.

It dominated the Bay of Grouville which, with its gently shelving beach sheltered from the prevailing winds, was the best landing beach in the island.

Throughout the medieval period whenever the English held Normandy the Islands enjoyed peace. When the French were in control the islands were placed on a war footing and the castle defences were updated.

The castle's position as the main fortress in the island was lost when cannons were introduced into warfare as this meant that the castle became obsolete, although attempts were made to upgrade the defences.

http://www.jerseyheritagetrust.org/sites/orgueil/history.html