Such a system was axed in 1997, when the EU’s Maastricht Treaty introduced free movement for EU citizens and under current rules, UK citizens queue at airports and other border crossings with those from European Economic Area countries — the EU, as well as Iceland, Liechtenstein and Norway - and Switzerland.

According to the Financial Times, “an ally of the prime minister” said yesterday (August 1) that “British-only” passport queues were to be expected when EU citizens lose the automatic right to enter the UK after the post-Brexit transition period ends in 2020.

“We will have left the EU and we won’t have free movement anymore,” the aide said.

Theresa May’s insistence on the reintroducing UK citizen-only queues was first reported by the Sun earlier this week, which claimed her to be in disagreement with home secretary Sajid Javid, who was concerned British-only queues would harm the efficiency of immigration checks.

A senior Downing Street source told the newspaper: “The [Prime Minister] wants separate lanes for British travellers as an important sign to voters that Brexit has happened and there are tangible benefits from it that everyone can see."

Addressing the subject of efficiency at immigration, the ally of May told the Financial Times: “We are acutely aware of the need to keep disruption to a minimum — it’s very much a work in progress.”

Taking questions from the home affairs committee last month, Javid acknowledged that EU citizens would lose the right to use ePassport gates because they would no longer have the right automatically to enter the country.

He did not mention UK-only queues being adopted during the session.

A Home Office spokesperson later said: “We are considering a range of options for the future immigration system and will set out more details later this year.”