SIR JOHN NOT QUITE A CHARACTER IN NETFLIX's THE CROWN

Just a note.  I was rewatching The Crown, which is an excellent series about the British Royal Family.  I know it cannot be "accurate" and must be considered fiction based on much of what is known about the Royal Family, but if you haven't seen it, well, try to. Excellent production values.  Historical content. Terrific acting. Truly an achievement for all involved.

In Season Two, Episode Four, which is about Princess Margaret's introduction to the photographer Antony Armstrong-Jones through a Lady In Waiting, she is invited to a dinner party attended by "unconventional" people.  Margaret has had a tough love life thus far, being unable to marry her first true love because he was a divorced man. She is starting to go nutty and so, to help her get out of the house (the castle) she attends this dinner party.

She notes that the poet John Betjeman is at the party.  She says, "Is it true he has two wives?"  and Armstrong-Jones says, "Better he has three."

Ever since I saw that, I've been wondering - WHO WAS THE POSSIBLE THIRD WIFE OF POET SIR JOHN BETJEMAN?  If you know, please leave a comment!