HMRC are operating an extortion racket on behalf of McBroon. McBroon decides how much he wants and sends his heavies to get the loot. Most of the time a written threat, in the form of a tax demand is enough to get the victim to part with their hard earned cash. Other times a visit is required with threats of prison. Muggers of old ladies in the street have more integrity.
Check out following site and see if you can spot the criminal activity. Demanding money with menaces is the clue:-
http://web.mac.com/nickmorgan/HMRC/tax-hell.co.uk