During his ill-fated marriage to Princess Diana, King Charles is said to have grown increasingly jealous of her massive popularity.
In the early days of their union, Charles would often be overshadowed by his wife, with crowds shouting to talk to Diana instead of the future king.
The apparent envy is said to have placed a great strain on the marriage, with Diana confirming his jealousy in her controversial Panorama interview in 1995.
"The pressure on us both as a couple with the media was phenomenal, and misunderstood by a great many people," she said. "We'd be going round Australia, for instance, and all you could hear was, 'Oh, she's on the other side.'
"Now, if you're a man like my husband, a proud man, you mind about that if you hear it every day for four weeks. And you feel low about it, instead of feeling happy and sharing it."
Claiming it caused "a lot of jealousy", she added: "A great deal of complicated situations arose because of that."
In recent days, there have been reports that history could be repeating itself, with one expert speculating that the new Princess of Wales had upstaged Charles and now-wife Queen Camilla.
Kate's unexpected appearance at the Chelsea Flower Show garnered far more buzz than when he and Camilla visited hours later.
However, royal expert Robert Jobson has explained that Kate in fact has her father-in-law's blessing to "steal the limelight" - and it's down to him now having the top job.
Writing for MailOnline, he explained: "Whilst it is Charles' head that wears the Crown, it is William, Catherine and their children that will steal the limelight. They are bound to. And it is right.
"This time, it will be with Charles's blessing – for he knows for monarchy to survive it must be relevant to the younger generation."
It comes amid William and Kate embarking on a new social media blitz after a big change to their Twitter and Instagram accounts.
One of the biggest changes is the addition of slick behind-the-scenes videos, with several posted over King Charles' Coronation weekend.
One, which was posted to their YouTube channel, even gave a sneak peek inside their Kensington Palace home, getting ready to attend the historic event.
But despite many fans seeming to love the glossy updates, royal correspondent Rebecca English has said there is some trepidation within those working for the royal household on whether it is the best way to promote the monarchy.
Speaking to the Daily Mail's Palace Confidential show, she explained: "The Waleses have been looking at this for a while and they have really ramped it up since Easter - how do we tell our story to younger people and how do we engage them and show people what we are doing?
"Not just us as a family but the work we are doing and the difference we are trying to make whether it is homelessness, mental health, education, or the environment.
"One of the ways they have decided to do this is to be a bit slicker with their social media because that is how young people consume their news nowadays.
"Now the jury is still out a little bit on whether this is the right way to do it because these social media clips are almost too well put together.
"So the jury is still out amongst the wider royal household but there is support for them trying to engage people in a different way."
