Prime Minister Theresa May will trigger Britain's divorce proceedings with the European Union on March 29, launching two years of negotiations that will reshape the future of the country and Europe.
On Monday May's government said her permanent envoy to the EU had informed European Council President Donald Tusk of the date when Britain intends to invoke Article 50 of its Lisbon Treaty - the mechanism for starting its exit after a referendum last June in which Britons voted by a 52-48 per cent margin to leave the bloc.
The EU said it was ready to begin the negotiations and within 48 hours of the trigger on March 29, Tusk will send the other 27 member states his draft negotiating guidelines, which means that talks could start in May.
Sterling fell half a cent against the dollar on what Brexit minister David Davis described as a move taking Britain to "the threshold of the most important negotiation for this country for a generation".
May hopes to negotiate terms that keep trade, financial and political relations with EU member states as close as possible after Brexit, but also satisfy eurosceptics in her Conservative Party who demand a complete break.
Talks on departing the prosperous club Britain joined in 1973 are likely to be the most complex London has held since World War Two.
With nationalism and anti-establishment, anti-immigrant sentiment spreading across Western Europe, the EU leadership in Brussels is anxious to avoid encouraging others in the 28-member bloc to bolt.
At the same time, May faces threats by Scottish nationalists to call a new independence referendum that could break up the United Kingdom and fears in Northern Ireland that a "hard border" with EU member Ireland will return after Brexit.
May succeeded David Cameron soon after the Brexit referendum, but delayed triggering Article 50 to give herself time to work on her strategy.
The referendum exposed geographical and social divisions in Britain.
Against the backdrop of trying to keep the UK together, May has a long wish list for the EU - the closest possible trading ties, security cooperation, regaining control over immigration and restoring sovereignty in various policy areas.
The EU has baulked at her demands, saying they amount to "having your cake and eating it".
May's government acknowledges its opening position is bold, and is also preparing for the possibility of crashing out of the bloc with no deal.