British Prime Minister Theresa May speaks to the media outside 10 Downing Street in London, Britain on May 24, 2019. Theresa May said on Friday that she will quit as Conservative leader on June 7, paving ways for contest to decide Britain's next prime minister. (Xinhua/Alberto Pezzali)

British Prime Minister Theresa May speaks to the media outside 10 Downing Street in London, Britain on May 24, 2019. Theresa May said on Friday that she will quit as Conservative leader on June 7, paving ways for contest to decide Britain's next prime minister. (Xinhua/Alberto Pezzali)

British Prime Minister Theresa May speaks to the media outside 10 Downing Street in London, Britain on May 24, 2019. Theresa May said on Friday that she will quit as Conservative leader on June 7, paving ways for contest to decide Britain's next prime minister. (Xinhua/Alberto Pezzali)

British Prime Minister Theresa May returns after speaking to the media outside 10 Downing Street in London, Britain on May 24, 2019. Theresa May said on Friday that she will quit as leader of the Conservative party on June 7, paving the way for the process of electing her successor. (Xinhua/Alberto Pezzali)

British Prime Minister Theresa May speaks to the media outside 10 Downing Street in London, Britain on May 24, 2019. Theresa May said on Friday that she will quit as leader of the Conservative party on June 7, paving the way for the process of electing her successor. (Xinhua/Alberto Pezzali)

British Prime Minister Theresa May speaks to the media outside 10 Downing Street in London, Britain on May 24, 2019. Theresa May said on Friday that she will quit as leader of the Conservative party on June 7, paving the way for the process of electing her successor. (Xinhua/Alberto Pezzali)