British Prime Minister Theresa May announced that her government will trigger Brexit negotiations by the end of March, putting the country on course to leave the European Union by early 2019.
The move will plunge Europe's second largest economy into two years of painful horsetrading with its EU partners, who have voiced deep frustration at the delay in setting a date to start divorce proceedings.
It was May's firmest commitment to a clear break with the EU since she became Conservative Party leader and premier in the political upheaval that followed June's shock referendum vote to quit.
"Britain is going to leave the European Union," May told the opening day of the Conservative Party conference in the central English city of Birmingham.
"There will be no unnecessary delays in invoking Article 50. We will invoke it when we are ready. And we will be ready soon," she said, referring to the article in the EU's Lisbon treaty setting out a two-year process to leave.
"We will invoke Article 50 no later than the end of March next year."
May said she would seek the best deal from the 27 other EU members, but told the conference she would not give a "blow by blow" account of her negotiating strategy, for fear of weakening Britain's hand.
European powers keen to dampen rising euroscepticism in their own backyards have taken a hard line with Britain, warning that informal negotiations cannot start before the two-year notification process is triggered.
May's announcement means the process will start before next year's crucial elections in Germany and France, with an uncertain impact on the polls in the EU's most powerful nations.
- 'Decide for ourselves' -
May's government and party is divided over whether to go for a "hard" or "soft" withdrawal from the EU.
"Hard" Brexit would mean quickly severing all links with EU institutions and pulling out of the single market, relying instead on World Trade Organization rules to trade overseas.
"Soft" Brexit would retain access to the single market in some form, but EU leaders have made clear that this would require continued free movement for EU workers into Britain.
Uncontrolled mass immigration from the EU was a major factor in Britain's historic vote to become the first country to leave the bloc after four decades of membership.
Brussels has insisted that if Britain wants free trade with the EU, it must also accept freedom of movement.
But May took a hard line in her speech, signalling that while she wanted free trade in goods and services, she would be prepared to leave the single market if necessary.
"We are not leaving the European Union only to give up control of immigration again," she said. "We will decide for ourselves how we control immigration."
- 'Welcome clarity' -
In another act designed to reassure anti-EU figures in her party, May also announced Sunday that a "Great Repeal Bill" would be introduced to scrap the supremacy of EU laws in Britain on the day of exit from the bloc.
The announcements by May -- who campaigned quietly for Britain to remain in the EU -- were welcomed by European leaders and Conservative eurosceptics alike.
EU President Donald Tusk wrote on Twitter that it brought "welcome clarity," adding that once Article 50 was triggered, the EU would "engage to safeguard its interests."
Leading Conservative eurosceptic MP Bernard Jenkin called May's comments "pitch perfect."
Many Conservative activists in Birmingham also praised her.
"She's been respectful of both those who voted to leave and the feelings of those who voted to stay," said one, Rachel Joyce.
"Pragmatically it's about the right time. She needs to line all of the ducks up before she triggers Article 50."
But Conservative MP Anna Soubry, who campaigned to stay in the EU, warned May's government against a "gung-ho" approach to activating Article 50 ahead of the French and German elections.
"The government should be pressing for a deal that keeps Britain open and engaged with Europe, including keeping us in the single market," she added.
May -- who will give the keynote closing speech at the conference on Wednesday -- starts the party conference in a strong position.
Opinion polls put the Conservatives well ahead of the deeply divided main opposition Labour Party under socialist leader Jeremy Corbyn.
But she has ruled out a general election before the next one is due in 2020, telling this week's Sunday Times newspaper it would "introduce a note of instability."