The stakes of any future Brexit deal increased today when the European Union's draft negotiation strategy outlined that Spain would be given a final say on how the deal affects Gibraltar.
The leaked negotiation guidelines set out this morning by European Council President Donald Tusk seem to give Spain the power to veto a deal between the UK and the EU if it is dissatisfied with the future of the British Overseas Territory, to which it has a long-standing territorial claim.
The relevant clause was reportedly added after pressure from Spanish diplomats.
After the United Kingdom leaves the Union, no agreement between the EU and the United Kingdom may apply to the territory of Gibraltar without the agreement between the Kingdom of Spain and the United Kingdom.
Gibraltar was officially ceded to Britain in 1713 after being jointly captured by the British and Dutch in 1704.
In a 2002 referendum putting the question of joint Spanish and British sovereignty to the territory's 30,000 residents, almost 99 per cent of the Rock's population rejected the idea.
When Britain joined the European Union in 1973, Gibraltar automatically joined too. Residents voted to Remain in the European Union by 96 per cent in last summer's referendum on the matter.
UK Prime Minister Theresa May made no reference to Gibraltar in Wednesday's notification of withdrawal from the European Union. Vice-president of the European People's Party Esteban González Pons told Spanish newspaper El Pais he considered the omission to be "very relevant". "Gibraltar isn’t part of the United Kingdom; it’s a colony like the island of St Helena," he said.
Bob Neill, chair of the Commons Justice Select Committee tasked with examining the relationship between the UK and its overseas territories, tweeted: "Gibraltar's friends in the UK will be watching this very carefully. There will be no sell out."