Reports of Theresa May’s political demise may have been exaggerated, with her spokesman revealing that, while her time as Conservative Party leader is set to come to an end on Friday, she will remain as prime minister until she “believes that someone else can command the confidence” of MPs.
British prime ministers are not directly elected by the people, with prospective candidates instead being invited to serve by the monarch, generally on the assumption that they can command a parliamentary majority or at least muster enough support on key issues to execute a legislative programme.
https://www.breitbart.com/europe/2019/06/06/interim-prime-minister-life-may-will-only-go-successor-confidence-mps/