The 1969 Gibraltarian constitutional order made it clear that the British would not impose a solution on the Gibraltarians and acknowledged their right to self-determination in their political future. Francisco Franco continued to insist that Gibraltar was territorially integral to Spain and, "in a fit of diplomatic pique", ordered the closure of the border in 1969. For the next 16 years, Gibraltar was reliant on an airlink with Britain for formal access to the outside world.
The closure of the border hardened Gibraltar's attitudes towards Franco and Spain more generally.
It is also ironic that the actions taken by Francisco Franco and Spain completely destroyed any potential for winning over the population and gaining support in either Britain or Gibraltar for transfer of sovereignty to Spain.... This natural tendency of the two populations to interact demonstrated the artificial division that had been created and continued to exist so long as Britain retained possession of Gibraltar. Instead, he demanded the immediate return of Gibraltar, initiated a newspaper campaign in which the entire population was characterised as criminals and individuals of dubious moral character, and imposed border restrictions that caused real hardship on the inhabitants.
A diplomatic stalemate persisted until after the death of Franco, when Margaret Thatcher's government initiated a political process that resulted in the Lisbon Agreement. It was a joint statement by the Spanish Foreign Minister, Marcelino Oreja, and the British Foreign Secretary Lord Carrington signed in Lisbon on April 10, 1980. Its preamble stated:
The British and Spanish governments, desiring to strengthen their bilateral relations and thus to contribute to Western solidarity, intend, in accordance with the relevant United Nations Resolutions, to resolve, in a spirit of friendship, the Gibraltar problem.
- Dodds, Klaus (December 2004). "Solid as a Rock? Britain and Gibraltar". BBC History: 18–21.
- William Godfrey Fothergill Jackson (1990). The Rock of the Gibraltarians: A History of Gibraltar. Gibraltar Books. ISBN 9780948466144. Retrieved 4 February 2011.
- George Hills (1974). Rock of contention: a history of Gibraltar. Hale. ISBN 9780709143529. Retrieved 7 February 2011.
- "Gibraltar: Little Territory, Lot at Stake". Archived from the original on 2011-05-15. Retrieved 2011-02-03.
- Garcia, Dr Joseph. "Political History of Gibraltar". Archived from the original on 2011-07-21. Retrieved 2011-02-03.
- Finlayson, Thomas James. "The Struggle for Democracy". Gibraltar Chronicle. Archived from the original on 2004-04-28. Retrieved 2008-10-21.