There are a number of islands around the coast of Scotland, Wales and England which have road networks. But,

Question

which is the only one of these islands to have a motorway on it? (And I do not mean Ireland!)

The ten points goes to the first correct answer.

Answer 1

According to this there are none!  So do tell..

http://www.12go.co.uk/motorways.cfm

Answer 2

Isle of Wight  

Answer 3

M275 at Portsmouth

Answer 4

Portsea Island off the Hampshire coast.