Princess Kate's tactic to keep William on his toes laid bare

Kate Middleton had a clever tactic to keep Prince William on his toes during their fledgling romance, according to a royal author.

"She played it very cool and at one point when William seemed to lean in to her, she pulled away," claimed royal author Katie Nicholl in her 2011 book, The Making of a Royal Romance.

Nicholl, a journalist and broadcaster, according to The Mirror, wrote: "She didn’t want to give off the wrong impression or make it too easy for Will."

"When I first met Kate, I knew there was something very special about her," William later said. 

"Then I knew there was possibly something I wanted to explore there, but we ended up being friends for a while."

A key moment in the couple's friendship turning into romance reportedly came in March 2002, when Kate wore a stunning dress at a charity fashion show. "It was clear to us that William was smitten with Kate," a friend told Nicholl of the night in question.

"He actually told her that she was a knockout that night, which caused her to blush."

Princess Kate reportedly began dating her future husband Prince William when the two were students at the University of St. Andrews.