Spanish police on patrol at both Gibraltar's port and airport – a post-Brexit proposal from the European Union (EU) – will undermine British sovereignty, according to the Chief Minister of Gibraltar.
Fabian Picardo told the latest episode of the BFBS Sitrep podcast it would be "absolutely unacceptable, for every moment of every second of every day, to think that there are Spanish law enforcement agents on the soil, the British soil, of Gibraltar".
"In practical terms, it would be exactly the same as permitting the French gendarmerie to handle immigration at Heathrow," he said.
"You might find that there is no difference, there's just a person there who checks your passport and lets you into the United Kingdom, but you wouldn't for one moment accept it because, of course, it would be the most heinous interference with your sovereignty.
"This is about much more than just the practicalities, this is about the underlying issue of British sovereignty being in violet in respect of Gibraltar and the most ferocious defenders of British sovereignty over Gibraltar will be the British Gibraltarian people of Gibraltar.
"And I can tell the European Commission now, we have been very respectful of them running up their mandate in the time that they needed in order to ensure that they did it in the way that they felt was appropriate.
"But we will not for one moment accept that they should think that they can trample over even the slightest and most minimal iota of British sovereignty as they go."
Mr Picardo's comments come after the European Union put forward a new framework for future negotiations, despite an agreement reached by the UK, Spain and Gibraltar, known as the New Year's Eve framework agreement, in December last year.
The British Overseas Territory is not covered by the UK's Trade and Co-operation Agreement and separate negotiations with the EU are set to take place to agree on a post-Brexit treaty.
"The mandate which the European Union has come up with is not faithful to the arrangements that the United Kingdom and Spain have put to the European Union. It almost seeks to start the negotiation again," Mr Picardo said.
"It is not a basis on which we can negotiate a treaty for the future."
So what happens now?
"As far as I'm concerned, this mandate is stillborn," said Mr Picardo.
"The European Commission will have to do a lot of work to ensure that they can produce a treaty after rethinking their mandate, that is faithful to the New Year's Eve agreement."
He added that the EU needed to "buck up its ideas and realise that there's no chance of this treaty actually happening" unless it was in line with the agreement reached in December.