Duchess Kate stars in video for kids' mental health

Who will speak out for children suffering from mental and emotional crises? Duchess Kate of Cambridge will, proving that her early nervousness about speaking in public is long gone.

Kate appeared in a brief (and rare) online video that dropped just after midnight Monday in the U.K. (7 pm ET), on behalf of a favorite child mental-health charity, Place2Be, and to mark Britain's first Children's Mental Health Week.

The video was recorded last week in a classroom at a children's hospital school she visited in the Beckenham district of London, which was not announced in advance nor photographed.

Looking radiant, her second pregnancy (she's due in April) just visible beneath her blue Jaeger tile-patterned silk shirt dress, Kate spoke confidently and with equal parts passion and compassion for children traumatized in childhood by bullying, grief, family breakdown, domestic violence and more.

Without intervention such trauma can led to depression, anxiety, addiction and self-harm, she said. And yet many still feel it is a sign of weakness to ask for help, she said.

"The stigma around mental health means that many children do not get the help they so badly need. This needs to change," she said. "A child's mental health is just as important as their physical health... No one would feel embarrassed about seeking help for a child if they broke their arm and we really should be equally ready to support a child coping with emotional difficulties."

Invoking husband Prince William, she called on Britons to talk openly this week about how to do better in combating children's mental-health problems.

Place2Be, for which Kate is the royal patron, is the leading U.K. provider of school-based mental health services for kids. It's one of several charities Kate has taken up that involve issues about children, such as combating addiction and hospice care for terminally ill kids.

She gets props on Twitter for taking on such sensitive matters.

"Through Place2Be I have seen the benefits of offering children support for their mental health in the safety of the school environment," she said in the video. "Both William and I sincerely believe that early action can prevent problems in childhood from turning into larger ones later in life."

When the former Kate Middleton married Prince William in April 2011, and became Catherine Duchess of Cambridge, she took on a job that included royal patronage, public appearances and occasional public speaking.

She was nervous and brief for her first speech, in March 2012, at a children's hospice in southeast England, but there was no trace of anxiety in this rare video appearance.