The hutches sit on flagstones.Is it built on concrete foundations Jaz? Cos foxes will easily dig under a fence. No matter how high. Our chicks would dutifully troop up the ramp into their wooden, locked, hen house at dusk. They were fenced into an outdoors coop with a normal sized fenced area using chicken wire at first, but we soon allowed them the run of the orchard, and some would come inside/sit on our laps on the patio.
They always had access to feed, but they also developed a taste for pasta, melons and tomatos. Nik and I would make them a cake of all 3 at Christmas!
The wire fence of the coop is buried about 6 inches underground.