Britain's Duke and Duchess of Cambridge have a "very special relationship".
The royal couple were observed by writer Penny Junior for her tome Prince William: Born to be King while on their Canadian tour last year.
Penny says the couple's behaviour is very different to that of William's father Prince Charles and his late mother Princess Diana of Wales.
"Their body language [was different]. With Charles and Diana there was none of that hand squeezing or looking at each other that William and Kate did on their tour," she explained to the UK version of OK! magazine.
"When William and Kate were sitting next to each other they were whispering and giggling and they clearly have a very special relationship - they are in love. Charles and Diana were not."
Penny also compared Prince William's mother Diana to Catherine. She says there are many similarities between the two women.
"There were many instances of déjà vu - seeing Kate and remembering how Diana had been that first time. I thought Kate was a natural born communicator, like Diana," she gushed.
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