It's a relationship that has already fuelled much speculation where The Crown is concerned.
The Netflix series The Crown has portrayed the long-running friendship between The Queen (Olivia Colman) and Lord "Porchey" Porchester (Joseph Kloska), with some even concerned that the new series would suggest they were more than friends.
The fifth episode of the season, entitled Coup, sees Elizabeth II question what sort of life she could have had if she wasn't monarch as the pair go on trips to aid their chances with their horse-racing endeavours.
But is The Crown suggesting any more than what history tells us of the pair?
In the new official book The Crown: The Inside History 1956-1977, historian and show historical consultant Robert Lacey writes: "Towards the end of Episode 305 a mildly jealous Prince Philip indecorously suggests that it was not just Her Majesty's racehorses that 'Porchey' was very keen on injecting - and the lifelong personal friendship that Elizabeth II enjoyed with Lord Porchester until his death aged 77 in 2001 has sometimes been the source of inneundo.
"But there is no historical basis for any suggestion of impropriety - and The Crown certainly has no truck with it."
He adds: "On their 1967 trip to Normandy, for example, Elizabeth and 'Porchey' were accompanied by his Anglo-American wife Jean Wallop, who remained of the Queen's closest personal friends until her own death in April 2019."
Lacey surmises: "The touching and unashamed intimacy enjoyed by Elizabeth II and Lord Porchester went back to the passion for horses they discovered they shared when they first got to know each other as teenagers.
"We have seen this relationship developing in previous episodes of The Crown, and 305 is the episode that makes it official."
That closes the book on that!
The Crown season 3 is available now on Netflix.
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