"She opens up a whole new audience for children's hospices," Grant Butland, who works with the princess, tells PEOPLE
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It may only have been a short note of support, but to the hospice movement, a recent letter from Princess Kate underscored her quiet power.

Kate, 33, underlined the “precious” moments that parents and children should ideally be able to have as they’re cared for in hospices.

Palace sources tell PEOPLE that Kate knew she would be at home bonding with newborn Princess Charlotte when Children’s Hospice Week came around but wanted to do what she could to add her voice to the ongoing campaign.

“She has a huge impact,” Graham Butland, chief executive of one of Kate’s key charities, East Anglia’s Children’s Hospices, tells PEOPLE.

“We were delighted when she became our patron because of the impact that it would have on EACH directly – and that continues,” says Butland. “The fact is, she has just raised the profile both nationally and internationally of children s palliative care.”

Kate has made speeches at hospices while on foreign tours and supported her locally-based EACH at home in the U.K.

“She opens up a whole new audience for children s hospices and children s palliative care,” Butland adds. “Just a short message reminding people of Children s Hospices Week is tremendously supportive of the whole movement.”

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While Kate may be having some time off from public duties while she looks after 10-day-old daughter Princess Charlotte and 21-month-old son Prince George, she is keeping in contact with EACH and other charities.

Butland adds that he “imagines” it will be six months before she is back publicly working.

“But that doesn t mean she s not interested in what s going on. We send regular updates about what s going on and she s always keen to know those,” he says.

And now she’s much nearer too “moving into our backyard, if you like, at Anmer Hall,” as Butland puts it. He and his charity are currently trying to raise $16 million (an effort Princess Kate helped kick off in November) to set up a new hospice, called The Nook, at Famingham Pygot, about 40 miles from Anmer Hall where she and Prince William are mainly based.

“I m hopeful that when she s back doing duties and working out of Anmer Hall that she ll continue to give us the superb support she s been giving us for the last three or four years,” says Butland.