R. H. Haigh & D S Morris 
Britain, Spain and Gibraltar 1945-1990 [PDF ebook] 
The Eternal Triangle

Since 1945 Gibraltar’s sovereignty has repeatedly been questioned. A strategic possession overlooking Africa at the mouth of the Mediterranean, Gibraltar is the victim of both history and geography and continues to be the barometer of Anglo-Spanish relations. Arguing that Gibraltar has played a much more proactive role in negotiations than is assumed, the book describes the objectives and actions of the Gibraltarians against the wider map of Anglo-Spanish relations.