Thorney island is effectively a peninsula that juts into Chichester Harbour in West Sussex. There is a military base on the island that has a runway, although it is currently a REME (Royal Electrical Mechanical Engineers) base. Large C-130 Hercules aircraft used to fly from here when it was an RAF base. It is separated by a channel that runs across the island/peninsula called the Great Deep. In the 2001 census it had a usually resident population of 1,079.