 Ross disagreed , reasoning this would only damage relations between Britain and Portugal , an undesirable prospect given the countries ' common membership in NATO , the European Free Trade Association and more . There was much at stake ; Britain enjoyed an annual £ 48 million trade surplus with Portugal , and Portuguese Railways was in the process of buying 50 diesel locomotives from English Electric . In the Azores archipelago , Portugal provided NATO with a strategically key air base , which was unprotected by treaty ; given the inclination , Lisbon might close it . 
