What is the origin of the idiom "Bob is your uncle" and when to use it?

The idiom "Bob is your uncle" is a British expression used to indicate that something is very easy to achieve or that things will work out smoothly. Its origin is believed to be linked to nepotism in British politics. In 1887, Arthur Balfour, a British statesman, was appointed as the Chief Secretary for Ireland by his uncle, Lord Salisbury, which led to widespread use of the phrase to suggest that political success can be as simple as having an influential relative.