Speaking at the inaugural summit of former US president Barack Obama's foundation, the Prince glowed with pride as he explained why he thought she had earned the moniker 'People's Princess'.
He said: "I think she had a lot in common with everybody, but she would also listen.
"(She put) her name and platform towards some of the big issues which had never been talked about before.
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"We suffer from this illusion, or reality I suppose, where some problems become so big no one wants to get involved.
"She was the one who wanted to change that.
"I will always look up to her as my ideal role model. Everything she did was having an impact, it was making a difference."
He added that he believed Diana had "rewritten the rule book" for the royals, and the role they play in society.
He said: "All the people she was working with would be incredibly grateful for her pushing those boundaries."