File:Square leg.gif

Map scanned from 'Doomsday, Britain after Nuclear Attack' by Stan Openshaw, Philip Steadman and Owen Greene Basil Blackwell, 1983 ISBN 0-631-13394-1

Fair Use
This is the only image I'm aware of showing the Square Leg targets, so I believe it's valid to use in the context of discussing those targets. It's also really incidental to the main content of the book it came from so unlikely to cause any loss of income to the publisher or author, if the book is still in print today.

I'm not aware of a full list of the Square Leg targets which would allow someone to create a free image showing the same information.