I heard the phrase “Bob’s Your Uncle” today on Mary Poppins. My wife has said it for years, mostly related to cooking (e.g. “You put the water in the pot, add some miso, and ‘Bob’s your uncle.'”) and to the ease and quality of the results.
Well, I wanted to find out the history of the phrase and it’s, of course, an interesting one:

The most attractive theory, albeit suspiciously neat, is that it derives from a prolonged act of political nepotism. The Victorian prime minister, Lord Salisbury (family name Robert Cecil, pronounced ) appointed his rather less than popular nephew Arthur Balfour to a succession of posts. The most controversial, in 1887, was chief secretary of Ireland, a post for which Balfour, despite his intellectual gifts, was considered unsuitable. The Dictionary of National Biography says: “The country saw with something like stupefaction the appointment of the young dilettante to what was at the moment perhaps the most important, certainly the most anxious office in the administration”. As the story goes, the consensus among the irreverent in Britain was that to have Bob as your uncle was a guarantee of success, hence the expression. Since the very word nepotism derives from the Italian word for nephew (from the practice of Italian popes giving preferment to nephews, a euphemism for their bastard sons), the association here seems more than apt.