Theresa May began her first full day as British prime minister Thursday under immediate pressure to implement Brexit, after stunning observers by picking gaffe-prone "Leave" campaigner Boris Johnson as her top diplomat.

EU leaders were quick to congratulate Britain's new premier, whose appointment brought some stability following three tumultuous weeks since the country voted to leave the European Union, but urged her to move quickly.

The result sparked turmoil on the financial markets and the Bank of England was meeting later Thursday to discuss whether to cut interest rates to ward off the risk of recession.

According to AFP, May appointed former cabinet colleague Philip Hammond as finance minister, who said he would meet central bank governor Mark Carney later in the day.

But she sprung a surprise by appointing Johnson -- the former mayor of London who had appeared consigned to the political wilderness after backing out of the Conservative leadership contest -- as her foreign minister.