Britain and Gibraltar have agreed a post-Brexit deal that would hand control of the territory’s border to Europe, The Telegraph understands.

David Lammy, the Foreign Secretary, was on the Rock on Tuesday night for talks over the final parameters of the agreement, which will see Gibraltar join the bloc’s Schengen free movement zone.

This means Britons arriving on the Rock will have to show their passports to Spanish or EU border guards when they land at the airport.

It will use a similar system to that at St Pancras station in London, where Eurostar passengers first pass through British Border Force agents, before French border guards check the passports on British soil to ensure a frictionless exit at the destination.

British officers are stationed in France and Belgium to allow travellers to leave the station without controls. 

This arrangement could give the Spanish, or EU border guards, any final say over who is allowed to enter Gibraltar, even if they have passed through Gibraltarian border guards.

After striking an agreement with Fabian Picardo, Gibraltar’s chief minister, Mr Lammy headed to Brussels on Wednesday to try and get the deal over the line with EU Brexit negotiator Maros Sefcovic and Jose Manuel Albares, Spain’s foreign minister.

Sources told The Telegraph that “it’s the closest we’ve ever been”. A Spanish foreign ministry source said: “As always, our aim is to move forward as much as possible and close the deal as soon as possible.”

The expected deal will see Gibraltar join the Schengen zone to keep its borders with Spain open. It would become an associate member of the passport-free zone, which encompasses 29 European countries and would allow the free flow of people between the Rock and Spain.

Concerns that deal could still collapse

This would allow some 15,000 Spanish workers to continue crossing the border every day, and Gibraltarians to regain the freedom of movement they used to enjoy as European citizens before Brexit.

However, the arrangement would mean that Britons arriving on the British territory will have to show their passports to Spanish or EU border guards when they arrive at the airport.

There are some concerns that the deal could still collapse in the final negotiations between Mr Lammy, Mr Sefcovic and Mr Albares because of Conservative opposition in both the UK and Spain.

A UK official said: “We’re not going to Brussels to rubber-stamp a deal. Hard negotiations in the room ahead on a number of sticking points.”

But sources were confident of the deal because they said the three sides were keen to avoid a repeat of a previous meeting involving Lord Cameron, the former foreign secretary, last spring, which collapsed without an agreement despite one being close.

British officials had been hoping to sell the deal in the media before its completion, but withdrew plans to avoid tempting fate.

But Suella Braverman, the Conservative MP and former home secretary, said: “Another surrender and a handover in all but name. This Government consistently undermines Britain, and it is absolutely unforgivable. The Falklands will be next.”

Ahead of the meeting in Brussels, Mr Picardo wrote online: “It’s time to try to finalise arrangements for lasting, stable relationship between Gibraltar and the EU/Spain which is safe, secure and beneficial and which protects our people and gives certainty to frontier workers with a view to delivering more prosperity for all in our part of the world.”