Prince Philip once threatened to leave Queen Elizabeth II because of backseat driving, which is the practice of providing helpful advice to the driver from a position safely behind them, according to Gyles Brandreth, a close friend and biographer of the late Duke of Edinburgh.
The Duke, according to Brandreth, was known for his love of driving fast - but his spouse, the queen, did share his enthusiasm. On at least one occasion, when the prince was speeding, his wife "yelped" at him to slow down, making the Duke threaten her with "booting her out the car".
"The queen was sort of yelping and drawing in her breath and flinching as he drove so fast. And Prince Philip turned to her and said, 'Look, if you do that once more I will put you out of the car'", Brandreth told BBC Today Programme.
When the queen was asked why she did not protest, given that she is the monarch, she responded: "Oh you heard what he said, and he meant it."
According to the biographer, the duke was known to be a "dynamo" in his young days, providing a sparkle in the young queen's eye, but "he could be impatient." Some things never change, as the occasions of the queen and her prince bickering while the latter was driving were reportedly not rare. Brandreth described the squabbles as "sweet but so unexpected."
During another such episode, the prince reportedly told the queen: "Oh, do shut up, you silly woman." That time, however, the monarch was not willing to put up with such a tone, retorting: "I am not a silly woman, I am the Queen."