Grosnez Castle is one of those enigmatic places. On the one hand, from the ruins we must deduce that a castle of some size was build on the Grosnez headland, and it must have been quite magnificent judging from the ornate carved stonework. On the other, we really don’t know exactly when it was built (probably around the 1340s or possibly later) nor when it was pulled down (almost certainly after it was captured in 1373 by the Duke of Bourbon during the 100 Years’ War – NOT during the French occupation in the 1460s as suggested by the information board at the Castle!). On every old map of the Island known to exist, even those which are over 500 years old, Grosnez Castle is described as being in ruins. We don’t even know exactly who built it or what its original purpose was – probably the Seigneur of St Ouen and as a place of temporary refuge in case of attack rather than a siege castle like Mont Orgueil in the east.
The one thing which is certain, however, is that its location is spectacular with views to all the other Channel Islands on a clear day. For that reason, when signal stations were build in the 19th century by General Don to communicate with troops across all the Islands, one was sited on the cliffs near the Castle.