Britain on Sunday announced a new fast-track visa scheme for top scientists, researchers and mathematicians as it prepares a new immigration system for life outside the European Union.

Prime Minister Boris Johnson revealed the plan just days before Brexit finally takes place on January 31.

Concerns about mass migration were a driving force in the 2016 campaign to leave the EU, and Johnson has promised to end free movement with the bloc.

But he said on Sunday: "As we leave the EU, I want to send a message that the UK is open to the most talented minds in the world, and stand ready to support them to turn their ideas into reality."

EU free movement will continue for 11 months after Brexit during a transition period designed to allow London and Brussels to agree a new future partnership.

The government hopes to introduce a new points-based immigration system on January 1, 2021, for EU and non-EU citizens, but the details are still being worked out.

The newly announced Global Talent visa system will come into effect from next month, to replace the Tier 1 (Exceptional Talent) visa.

Only around 550 of the old visas were issued in 2018-19, well below the cap of 2,000, and officials hope the new, uncapped scheme will be more enticing.

It is open to a wider range of applicants, and offers an easier route to settling in Britain.

The government also unveiled an extra $392 million (356 million euros, £300 million) to fund "experimental and imaginative mathematical sciences research" over the next five years.

"The UK has a proud history of scientific discovery, but to lead the field and face the challenges of the future we need to continue to invest in talent and cutting-edge research," Johnson said in a statement.