Britain began an uncertain future outside the EU on Saturday, as it gears up for gruelling negotiations on future relations with the EU after the historic end to almost half a century of membership.

There was joy and sadness on Friday night as the EU’s often reluctant member became the first to leave an organisation set up to forge unity among nations after the horrors of World War II.

Little has changed yet as the UK is now in an 11-month transition period agreed as part of the divorce.

Britons will be able to work in the EU and trade freely – and vice versa – until December 31, although the UK will no longer be represented in the bloc’s institutions.

But legally Britain is out, with attention now turning to what are set to be tough talks with Brussels this year on the future relationship.

British newspapers reported late on Saturday that the government was readying for a bruising battle.

The eurosceptic Sunday Telegraph said Prime Minister Boris Johnson had already become “privately infuriated” at perceived EU attempts “to frustrate a comprehensive free trade deal”.

A leaked memo from Foreign Secretary Dominic Raab orders UK diplomats to make an immediate break with former European allies, in ways such as not sitting alongside them at international summits, the Sunday Times said.

It instructed them to “adopt a stance as a confident independent country”, the paper added.

British voters backed Brexit by a narrow margin in a 2016 referendum, sparking several years of domestic political gridlock about how, or even whether, to deliver it.

Johnson – whose decisive December election victory finally paved the way for Britain’s long-stalled departure – marked the occasion by holding a private party in his Downing Street office.

A clock projected on the walls outside counted down the minutes to Brexit becoming a reality at 11pm (2300 GMT) – midnight in Brussels.

In a televised address to the nation, the British prime minister hailed a “new era of friendly cooperation”, acknowledging there could be “bumps in the road ahead” but predicting the country would make it a “stunning success”.

Thousands of people waving Union Jack flags packed nearby Parliament Square and sang the national anthem to herald the occasion.

But Brexit has unleashed deep divisions in British society, with many fearing the consequences of ending 47 years of ties with their nearest neighbours.

Some pro-Europeans, including many of the 3.6 million EU citizens who have made their lives in Britain, marked the occasion with candlelit gatherings.

There was a sombre atmosphere on one of the last ferries to leave the European mainland pre-Brexit and make the 42km journey across the Channel.

“It’s very depressing what’s happening today,” said Alessio Bortone, an Italian who has lived in Britain for 10 years.