Long before there was a castle, the hill above what is now St Sampson's Harbour had a double ditch and bank, a fortified Iron Age site from somewhere between 500 and 600 BC. Archaeologists have found pottery from that period under both the medieval outer bank and beneath the fourteenth-century military buildings inside the walls. The hilltop made obvious sense as a refuge. To the south and east lay the sea; to the west, a tidal channel called the Braye du Valle once cut the entire northern part of Guernsey off from the rest of the island at high water. The Iron Age fort here is unique in Guernsey for its double bank, a sign that the people who built it took the threat from the sea seriously enough to dig twice.

In 1061 pirates landed and pillaged Guernsey. The islanders complained to Duke William of Normandy, the same man who five years later would conquer England. William sent a knight, Sampson D'Anneville, who drove the pirates off with help from the local monastery. As thanks, D'Anneville and the monks divided half the island between them. The monastery's portion, Le Fief St Michel, included the hill above the harbor, and the monks built a castle on it as a refuge for the local population the next time pirates came. They called it the Castle of Saint Michael. During the English Channel naval campaign of 1338-1339, the French captured the castle and put its defenders to death. They held the island until the Battle of Sluys in 1340 crippled the French navy. In 1372 the Welsh claimant Owain Lawgoch led a French free company against Guernsey, killing four hundred islanders in the militia. The poem written about that fight, La Descente des Aragousais, called the castle the Chateau de l'Archange.

After the medieval centuries the castle settled into a long late life as a coastal artillery position. The American Revolutionary War, by making France a British enemy again, prompted new barracks and ramparts. The French Revolution brought one 24-pounder and two 9-pounder cannons to the walls and six thousand Russian troops to Delancey alongside as part of the European coalition against Napoleon. Disease did what the French had not, and the Russian graves at Vale Castle date from that winter. By the nineteenth century the castle was a backdrop more than a defense. Francis Grose engraved it in 1786. Joseph Mallord William Turner sketched it. Victor Hugo wrote it into Toilers of the Sea in 1866. The whole site was listed as a Protected Monument on 26 March 1938, just in time for a war that would treat it as functioning fortress again.

The Germans arrived in June 1940 and stayed five years. They saw the castle the way every previous occupier had, as the obvious hill from which to defend the eastern coast, and they fortified it. Tobruk pits, machine gun positions, a personnel shelter, a searchlight passage, a field gun emplacement: the bunkers are still there, threaded through the medieval curtain walls. Today the castle is open to the public without charge except on event days. The Vale Earth Fair, a music and arts festival, has been held here for more than forty years, the bass lines bouncing off the same walls that once echoed with cannon. You can walk through the German trenches, look down on Bordeaux Harbour, and stand a meter from where Russian soldiers were buried two centuries ago. The hill keeps adding layers. The view it watches has not really changed.