“The U.K. has had territorial control over Gibraltar, which sits off the southwestern coast of Spain at the strategic entrance of the Mediterranean, since 1713. Britons have essentially been fighting with the European continent about its status for at least that long. More recently, the Spanish government threatened to impose border-crossing fees and control airspace to try to rein in those who live and pay taxes on the British island but work in Spain. Gibraltar dropped 70 massive blocks of concrete in prime Spanish fishing waters nearby as retaliation.”
Source: In the Brexit Divorce, Who Takes Custody of Little Gibraltar? – The Daily Beast