This castle is something of a mystery because it was dismantled piece by piece. Unfortunately there are no records of this happening nor of the castles’s construction.
We can confidently say it was a ‘bow and arrow’ castle because the two bastions on either side of the gate have arrow slits. It also had machicolations – extensions that overhung the walls – parts of these were found in the ditch, so it is likely to date from the 14th century when this type of defence became common in Northern Europe. Because there is no well here, it would not have been able to withstand a long siege, so the castle would have simply been a ‘castle of refuge’, one of a number situated around the island.
It is thought it was built sometime around 1327, when Sir John de Roche came to Jersey to inspect and strengthen the defences. In the years following this, the Hundred Years War was taking place and the island was constantly being attacked by the French
So who took the castle down?
It is possible it was here in 1373, when Bertrand du Guesclin raided the island. He was accompanied by the Duke of Bourbon, whose standard bearer wrote:”We arrived in Jersey, where there are two castles. The Duke attacked one, and the Constable attacked the other.” We know that du Guesclin attacked Mont Orgueil Castle, was Grosnez Castle the one that the Duke of Bourbon attacked? We also know that the Duke captured the castle he attacked.
There is a gulley to the north west of Grosnez known as Le Creux aux Francaises. Is this where the Duke attacked, at the back of the castle at the weakest point? And did he destroy the castle to prevent it being used again?
Or was the castle demolished in the period between 1461 and 1468, during the Wars of the Roses, when the island was occupied by the French? The French were allies of the Lancastrians while the de Carterets, who were Seigneurs of St.Ouen’s Manor, favoured the Yorkists.