London - A brave new world or a dangerous leap into the unknown? After nearly 50 years of integration with Europe, Britain starts an uncertain new chapter on January 1.

- What changes on January 1? -

Britain formally quit the European Union in January this year but has continued to observe all its rules during a transition period.

That half-way house ends at 2300 GMT on December 31. So from 2021, it will stand on its own, for better or worse.

If the two sides can secure a new trade deal in the time left, that will smooth the path by lifting the prospect of tariffs and quotas for cross-Channel goods, from cars to lamb.

Without a deal, imports and exports face serious disruption with the abrupt return of barriers that have not existed for decades.

EU chief sees 'progress' on Brexit talks but work needed

There are fears that certain foodstuffs and medicines could run short.

But even with a deal, the future won't be seamless.

UK exporters will still need to file reams of new customs paperwork to prove their goods have authorisation to enter the EU's single market.

Britain is urging business to be ready either way but industry players say the government has failed to deliver vital IT systems and support staff in time, heightening the risk of chaos after January 1.

Britain-EU relations

- What is Global Britain? -

Brexiteers argue the EU has held Britain back through onerous regulation and it can now embark on a buccaneering new mission to support free trade around the world -- "God's diplomacy", according to a February speech by Prime Minister Boris Johnson.

But if heaven was listening, it had other plans in mind: a month after Johnson's speech, Britain was forced into national lockdown by the coronavirus pandemic.

If the world ever gets back to normality, the idea is that Britain will not shrink inwards after Brexit but will look outwards, as far afield as a free-trade pact with Pacific rim countries.

"Now Global Britain is back, it is time for the makers, the doers and the innovators to help us write our most exciting chapter yet," International Trade Secretary Liz Truss declared in October, touting UK exports of everything from clotted cream to robots.

Key events in the Brexit process

Truss has signed a post-Brexit trade deal with Japan, and is negotiating others with the United States, Australia, Canada and New Zealand -- Britain's partners in the "Five Eyes" collective of English-speaking intelligence powers.

Further deals in the pipeline will cover 80 percent of overseas trade by 2022, according to the government, which has shaken up the Foreign Office to integrate aid and development into Britain's diplomatic agenda.

- What about at home? -

Johnson's pitch to voters in last December's general election was to "get Brexit done" and focus both money and attention on parts of the country that have failed to benefit from London's finance-driven growth.

That "levelling up" agenda to bring new investment such as high-speed rail to northern England has been side-tracked by the pandemic.

Map of the exclusive economic zones surrounding the UK and neigbouring states 

But the government insists its long-term goals remain in place and that membership dues sent to the EU will be better spent at home.

Some Brexiteers want a radical overhaul of Britain's economic model, to turn the country into "Singapore on Thames" -- a lightly regulated, lightly taxed rival to supposedly sclerotic Europe.

Yet the government stresses that any free-trade deals won't sacrifice its "red lines": the state-run National Health Service, food standards and UK farming.

All of those sacred cows could be carved up if the United States forces post-Brexit Britain to yield the same kind of concessions on trade that the world's most powerful economy has negotiated elsewhere.

Factfile on the Northern Ireland Good Friday agreement

And Joe Biden's election as US president could restrict Johnson's plans to bind Northern Ireland into the post-January 1 UK internal market, free of EU influence.

By Jitendra Joshi