"Rats have been spotted around the outside of the kitchen areas which clearly isn’t ideal," a source told The Sun on Saturday. "Staff, particularly kitchen workers, were given elementary training in how to stop them spreading."
The queen was reportedly "horrified" that rodents were infesting the palace.
"Obviously hygiene is a priority, as are simple things like shutting cupboard doors and sweeping away any crumbs or bits of food," the source said about fixing the problem.
Regardless, they also added, "There isn't a huge amount that can be done."