The Spanish have seized the opportunity presented by the UK's withdraw from the EU to attempt to gain some or maybe even all, control of the Rock. Long a dispute between Spain and the UK, Gibraltar itself, much like the Falkland Islands, which are also British Overseas Territories, have always, always, always voted to remain dependent upon the UK.
Gibraltar is tiny. 6.7km. Population 30,000. If it was in the UK it would be the same size as Windsor. or Pontypridd or Motherwell. Gibraltar was captured in 1704 from the Spanish when that dying superpower empire's efforts to peacefully pass control of its global empire to various factions failed.
Gibraltar was formally transferred to British control in the peace treaties that ended the wars of Spanish Succession in 1713. And there it has remained, seriously annoying the Spanish, ever since.
During WW2 Gibraltar, guarding the 8 mile gap between the Mediterranean and the Atlantic, was the most important 2.5 miles in the world. The significant Italian navy couldn't get out. The less significant, but still powerful German navy couldn't get in. And whether the Vichy French navy [the Toulon navy alone was the size of the German navy] was sunk or switched sides to the axis, was far less of an issue if it couldn't get free from its lake. The Allied bottle of Alexandria and Port Said had its cork at Gib.
A huge fortress naval base. Unlike Singapore properly defended. But like Singapore only really vulnerable to an attack from land. The 1940 fascist Spanish leader general Franco was promised Gibraltar if he allowed and assisted a German led attack on the base. He declined.
Gibraltar's referendum decision to reject Spanish influence in 1967 led to the permanent closure of the border. Something that could easily occur again now. It was only reopened through pressure from the EU and UK when Spain wanted to join the EU. The border was reopened in 1985 on Spain's accession.
Gibraltar has voted overwhelmingly for both UK sovereignty and EU membership.
It may not be able to have both.
The UK will almost certainly ignore any Spanish claims on Gibraltar. Reject any sort of borders or controls that will not apply to the UK as a whole and transfer no powers to Spain. or to the EU, the UN or any other made up seemingly benevolent but ultimately malevolent transitional European body that is conjured into being.
The EU knows this. Which is why its happy to encourage the Spanish to kick off. It can use the issue to extract a concession or two and then sop the Spaniards with some UK fishing waters or something later on.
Its a tough one for the UK. It has to be a red line for May. And I'm sure it is.
BUT .. Is there another way to solve the problem?
Too tiny for a country. Even Andorra is double the population. Too reliant on Spain's border to ignore them. Gibraltar needs a backer. And it could get one in the shape of the EU itself.
Monaco is a principality. It is not a formal EU member. But it does share in the customs union and border controls and is a user of the Euro. But it is definitely NOT in the EU. As anyone who experiences its zero percent internal corporation tax will appreciate.
{unrelated Corbynism : Monaco's low tax, low wage, edge of Europe status gives its citizens the highest standard of living in Europe.}
Monaco is administered by France in much the same way that Gibraltar is by Britain. In that it really isn't and they can do what they like on the understanding that the home nation can make use of the convenient backdoor loopholes for its own ends as and when it wants.
Liechtenstein. San Marino. Andorra. Vatican City and Monaco are all micro states with some EU involvement. All are completely sovereign but are all dependent on another major power for their defence. And this is a problem for nobody at all.
Gibraltar could demand microstate status, like the others. Agree to taking the Euro and enjoying same agreements those anachronistic nations have with the rest of the EU.
Worth a shot?