Theresa May formally steps down as leader of UK

File photo taken on Oct. 4, 2017 shows British Prime Minister Theresa May walking to the stage to deliver her keynote speech on the last day of the Conservative Party Annual Conference in Manchester, Britain. Newly-elected Conservative Party leader Boris Johnson took office as the British prime minister on Wednesday amid the rising uncertainties of Brexit. The latest development came after Theresa May formally stepped down as the leader of the country and Johnson was invited by the Queen to form the government. (Xinhua/Han Yan)