Britain and Spain have been sporadically at loggerheads over Gibraltar since 1704. In 1967 the territory held its first-ever referendum, producing a resounding vote in favour of British sovereignty.
The Spanish dictator, General Francisco Franco, began a campaign to force negotiations on the future of Gibraltar in the early 1950s, claiming that not only was British control of the territory since 1704 akin to colonisation, but that he had also been promised the rock by Winston Churchill during the second world war in return for not attacking British interests, writes Ian Searcey.
Both claims were dismissed by the British, but by 1966, under pressure from the United Nations, Spain and the UK began formal talks about the future of Gibraltar that would eventually lead to the first-ever referendum on the sovereignty of the territory.
By the time the vote came around on 10 September 1967, the electorate was presented with a simple choice: to accept Spanish sovereignty or retain the link with Britain and the crown.
Read more: why are we still arguing about Gibraltar?
As there was no sign within Gibraltar of any popular or political movement pressing for an end to British rule, and because civil liberties in Spain under Franco were restricted, it was widely believed that the Spanish claim had little chance of success.
In the end, 44 people voted for the first option, to accept Spanish sovereignty, while 12,138 (a resounding 99.34 per cent of the electorate) voted to stay British.
Sandy Gall reported for News at Ten on the joyous celebrations following the result, and on the reaction of local politicians, including Chief Minister Joshua Hassan and Governor Gerald Lathbury.
Not long after the vote, the Spanish government began to restrict movement between Spain and Gibraltar, and by 1969 it had effectively closed the border, stopping supplies entering by road and preventing Spanish workers from crossing over to work. Despite Franco’s death in 1975, the border was only fully reopened in 1985.
To mark the importance of that historic referendum in 1967, Gibraltar National Day has been celebrated on 10 September, since 1992.