What rights would British expats have under international law?

Asked what would happen to expats in the event of Brexit, a Leave.EU spokesman said: “Expats rights will be grandfathered due to the Vienna Convention.”

The Vienna Convention of 1969 states that people keep the rights that they once exercised under a treaty, even if that treaty is later terminated.

Therefore expats in Europe would retain their “acquired right” to stay there, but it would not apply to people who move abroad in the future.

Mr Smith said that these “acquired rights” include British expats’ rights to live in another country and own property there.

But he said: “They are quite basic. The rights do not cover healthcare or benefits. That is the legal view of the legal profession.”