She will start at a textile factory in Ayrshire before visiting young parents in Newcastle, meeting farmers in Northern Ireland, businesses in Wales, and European Union citizens in west London.
As now agreed in the draft withdrawal treaty, the official moment of European Union departure will be 11pm United Kingdom time on 29th March 2019.
"As stated by the European Commission in its notice to stakeholders on European Food Law in relation to the UK's withdrawal from the EU, the Commission's position is that United Kingdom exports to the EU27 will face veterinary inspection as any other third country does today".
As she visited parts of England, Scotland, Wales and Northern Ireland yesterday, her key message is one of unity for all those who voted for or against Brexit in the June 2016 referendum.
Northern Ireland will be her next stop, for lunch with farmers near Belfast before meeting Welsh business owners in Barry, then returning to London in time for tea with a Polish group.
Speaking ahead of her trip, Mrs May said: 'Having regained control of our laws, our borders and our money, and seized the opportunities provided by Brexit, the UK will thrive as a strong and united country that works for everyone, no matter whether you voted Leave or Remain'.
She continued: "We're clear that when powers come back to the United Kingdom, when we leave the European Union more powers will be devolved to the Scottish Government, but we want to ensure as we do that that people, businesses here in Scotland are able to continue to trade freely across the whole of the United Kingdom today, that's what we're talking to the Scottish Government about".
Mrs May insisted that each of the devolved administrations will see "an increase in their decision-making powers" as a result of the return of responsibilities now exercised by the EU.
March - Official level talks continue in Brussels - including on the issue of the border between Northern Ireland and the Republic.
Some in the British parliament still believe it is premature to presume that the United Kingdom definitely will leave in a year's time.
Blair, who was Britain's premier from 1997 to 2007, believes Brexit to be a giant strategic mistake and is a leading advocate for giving voters an opt-out.
A ComRes opinion poll published on Thursday showed 44 percent of people thought the government's handling of the negotiations had been "a total shambles".
But Foreign Secretary Boris Johnson said that "a glorious view awaits" Britain when it finally quits the EU.
She said: "Let's be clear, there is no power grab, we are not taking back any of the powers that are now devolved to the Scottish Government, indeed the Scottish Government will be receiving more powers as a result of us leaving the European Union".
"Like an unstoppable express, we are heading for Brexit, and frankly my friends, we can't arrive soon enough", he wrote.