I'll believe this when Queen Dick takes the throne!!
I say this because of the BBC, (so that's all right then?)
In the course of watching a programme on the every popular goggle-box yesterday evening I learned something, maybe two or three somethings, new. Among all this oh-so-newness I learned that the phrase, "When Queen Dick takes the throne." is just one example of a means of circumventing the use of the word, 'never', way more definite than the mere, "Once in a blue moon."
Another phrase used in this way was "When Dover meets Calais."
Where does all of this leave me? I am for learning a something new each and every day, but I am a little put out that what is learned today does no more than make a mockery of yesterday.

Ignorance is bliss, bliss is happiness, I am happy...to draw your attention to the possible connectivity in the foregoing.