Portsea Island (Portsmouth)

A flat island between Portsmouth and Langstone Harbours. Much of it is occupied by the city of Portsmouth including Southsea, and it is cut off from the mainland via a small channel. There is only a motorway, two roads and a railway which link it to the mainland, making Portsmouth the only place in the UK with 'Out of City' signposts. The island has a population of over 145,000 making it the largest island off the UK by population.