Her Majesty's Revenue and Customs. Roughly speaking, revenue being taxes on what you earn, and customs being taxes on what you buy.

There used to be separate departments for each, but they were merged years ago. This was a slightly odd move, as the revenue were people who were good at doing very detailed analysis of paper trails, whereas customs were people who were good at kicking down smugglers' doors.

Isn't that a logical move? Allow a single department to both gather and act on the information, rather than disparate departments that have to try to work together?