May, 59 assumed office after an audience with Queen Elizabeth and drove straight to her new home of 10 Downing Street, vacated hours earlier by David Cameron.

“We will rise to the challenge. As we leave the European Union we will forge a bold new positive role for ourselves in the world, and we will make Britain a country that works not for a privileged few, but for every one of us,” she said.

Cameron stepped down after Britons rejected his entreaties and voted to leave the EU in a referendum last month, severely undermining European efforts to forge greater unity and creating economic uncertainty across the 28-nation bloc.

May must try to limit the damage to British trade and investment as she renegotiates the country’s ties with its 27 EU partners. She will also attempt to unite a divided ruling Conservative party and a fractured nation in which many, on the evidence of the vote, feel angry with the political elite and left behind by the forces of globalisation.

Acknowledging the struggles faced by many Britons, May declared: “The government I lead will be driven not be the interests of the privileged few, but by yours. We will do everything we can to give you more control over your lives.

“When we take the big calls we’ll think not of the powerful but you, when we pass new laws we’ll listen not to the mighty but to you, when it comes to taxes we’ll prioritise not the wealthy but you.”

The United States congratulated May and said it was confident in her ability to steer Britain through the Brexit negotiations.

“Based on the public comments we’ve seen from the incoming prime minister, she intends to pursue a course that’s consistent with the prescription that President Obama has offered,” White House spokesman Josh Earnest said.

An official photograph showed May curtseying to a smiling Queen Elizabeth, for whom she is the 13th prime minister in a line that started with Winston Churchill.

She is also Britain’s second female head of government after Margaret Thatcher.