Kate's Unseen Work That She Does Which She Shares With Diana 

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The \'Unseen Work\' Princess Kate Shares with Princess Diana

Princess Diana in 1985 (left) and Princess Kate

Princess Kate is opening up about her little girl Charlotte Elizabeth Diana – and how she\'s carrying on the most loving traditions of William\'s mom.

for an inside look at how Kate is honoring the legacy of her mother-in-law, Princess Diana, only in PEOPLE!

Princess Diana championed many important causes over the years – including bringing awareness to HIV/AIDS, helping homeless and disabled people and shining a light on the issue of landmines. She also focused on the struggles of those with mental health issues.

And it\'s a cause that is also very important to Princess Kate.

For Diana, who died in 1997, "the day-to-day unseen work was largely mental-health-oriented," Patrick Jephson, her former private secretary, tells PEOPLE in this week\'s cover story.

"If you look at the statistics, the causes that Diana spent most time on was drugs and mental health."

Peter Fonagy, CEO of the Anna Freud Centre, which Kate supports, says the royal mom of two is "making the same critical contribution as Princess Diana made about AIDS."

She and husband Prince William are "destroying the myth that says that mental health issues are so hopeless and that there is nothing we can do about it."

For more on how Princess Kate is following in Diana\'s footsteps, pick up the latest issue of PEOPLE, on newsstands Friday.

Diana\'s friend Rosa Monckton also supports Kate\'s efforts.

"Anything that facilitates that conversation is a very good thing. In that sense, it is very similar to what Diana did with AIDS," she says.

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, says William and Kate are on their way to achieving the same level of impact.

"With Diana, there was a bedrock of routine day after day, unspectacular hard work. Cold, rainy nights in northern industrial towns visiting abused mothers or a hostel or a semi-conductor factory in the rain. It builds a reservoir of goodwill that buys you a bit of feasibility when there is a problem."

magazine, adds, "Kate wants to be the People\'s Princess, too. This is why she\'s been quite gentle in trying to find a role for herself, which she has now found.

"Diana certainly didn\'t find it straight away. It was a long time before she could make a difference to the things she was supporting."

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