The Average Cross-over Age From Leftism to Conservatism. On the Brexit vote:

Source: Politico

As a common political truism says, in various guises attributed to various well-known figures:

If you’re not a socialist before you’re twenty-five, you have no heart; if you are a socialist after twenty-five, you have no head.

or

If you aren’t a liberal when you’re young, you have no heart, but if you aren’t a middle-aged conservative, you have no head.

Currently in the UK the average cross-over age seems to be 34:

hat-tip Matthew