Answer: A British Prime Minister
A phrase commonly used in British English that is used by families of British and Commonwealth descent in other countries is "Bob's your uncle." The wording roughly corresponds to the American phrase "Piece of Cake" and implies that things will be easy no matter what instructions you have just received or what your chances are.
While "Piece of Cake" seems to be a pretty simple etymology ̵
It often turns out that your Uncle Bob is the Prime Minister of the United Kingdom. Already in 1887, then-Prime Minister Robert "Bob" Cecil appointed his nephew Arthur Balfour General Secretary for Ireland. The move surprised the public and the general attitude was that regardless of the young politician's qualifications, the most important thing was that Bob was his uncle. The whole event apparently gave the impression that "Bob's your oncle" has been a British phrase for a century and has changed.