The Queen has a big problem with moles at Sandringham, where there are more than 20,000 acres of ground for them to burrow through.
But Mr Williamson has to obey one royal request - he's not allowed to use poison to kill the moles - in case the corgis eat it by mistake.
So Mr Williamson lays traps in the moles' tunnels instead, which is a standard way to kill the garden pests.