There has been an escalation in tensions between Gibraltar and Spain in recent weeks following a number of alleged Spanish incursions into the British territory .On Sunday, Spain) fee to enter and leave Gibraltar through its border post.
In response, the Foreign Office voiced concerns and said Britain would not compromise its sovereignty over the Rock.
Below are some key events in the past and recent history of the dispute.
Gibraltar has been a British territory for 300 years since Spain ceded it under the Treaty of Utrecht in 1713. The treatysays the territory is Britain's "to hold forever, without any impediment or exception whatsoever".
Spain has since reasserted a claim to sovereignty over the Rock which stands on the southernmost tip of the Iberian peninsula.
The UK Government has made clear that it will not negotiate over sovereignty as long as residents want to remain British.
In 1967, a referendum was held and residents of Gibraltar overwhelmingly voted for continuing their association with Britain.
In 1969, the frontier between Spain and Gibraltar was closed by Spanish dictator General Francisco Franco in pursuit of his claim for the territory. It resulted in friends and families making a day-long journey by sea to visit each other.
Gibraltarians were granted full British citizenship in 1981.
In 1981, King Juan Carlos of Spain rejected an invitation to attend the wedding of the Prince and Princess of Wales over the ongoing dispute and anger over the royals' plan to visit the Rock on their honeymoon.
In 1983, Spain reopened the border gate for pedestrians only. Two years later it opened fully.
In 2002, a referendum revealed 99% of residents opposed the prospect of Britain and Spain sharing sovereignty over Gibraltar.
Britain, Gibraltar and Spain signed up to the Cordoba Agreement in 2006 which included deals on issues like border crossings and access for flights.
In July 2009, a Spanish minister visited Gibraltar for the first time in more than 300 years. But Spain said Miguel Angel Moratinos' visit did not signify any change to its claim to the Rock.
The Earl and Countess of Wessex visited Gibraltar in 2012, as part of the territory's Diamond Jubilee festivities. As a result, Spain's Queen Sofia cancelled a visit to the UK.
June 2013, David Cameron protested to his Spanish counterpart after a "totally unacceptable episode" when shots were fired at a jet skier off the coast of Gibraltar.
In July, Foreign Secretary William Hague raised "serious concerns" over claims Spain was deliberately engineering lengthy delays at the border with Gibraltar.
On August 5th, Spain's Foreign Minister Jose Manuel Garcia-Margallo said it was considering a 50 euro (£43) fee to come through its border post with Gibraltar.
Gibraltar's chief minister Fabian Picardo has accused Spain of acting like North Korea and "sabre-rattling" over the country's new hard-line stance.
Source: Gibraltar.gov and Press Association