Prime Minister Theresa May will promise Britain bright prospects outside the European Union on Thursday when she tours a country still deeply divided about its future as the countdown to Brexit starts its last 12 months.

Britain will leave the European Union at 2300 GMT on March 29, 2019, severing ties that helped define its national identity, its laws, and its international stature over 46 years of integration with European neighbors.

On Thursday, May will meet voters in England, Scotland, Wales and Northern Ireland — a whirlwind tour designed as a rallying cry for the union between the four nations, and to paint a positive post-Brexit vision. In the 21 months since the referendum vote, May, who became prime minister in the resulting political chaos, has struggled to unite the country behind a single vision of Brexit.

The world’s sixth largest economy caused a major global shock in 2016 by narrowly voting to withdraw from the EU after a fevered referendum campaign that sharpened regional divisions, pitted young against old, and exposed a deep distrust between voters and the political establishment.