This is a plum.
If you spoke with a plum in your mouth it would be quite difficult and make a strange sound. In Britain, there are lots of different accents that define not only a person's region but their social class. The upper class, and above all, the aristocracy, speak with a plum in their mouth. No more so than the Queen.
Here is a remarkable film of the Queen's annual Christmas speech from 1957, interesting not only for the accent but for the content.
Notice the pronuciation of the word often, pronounced orftn. The Royal family is also know for using archaic forms such as the pronoun 'one' instead of you.
'When one goes abroad, one orftn struggles to get a corpy of the Times.'
It's true marm, one does.
So here goes - is one ready? It's the first one, televised from Sandringham in Norfolk, one of the Royal family's many homes. Well, one's awfully rich marm.