The popular Royal said it takes great strength to talk about mental health and if those "in the thick of it" do not speak up, others will not.
London Ambulance staff members spoke to Prince Harry about their everyday encounters with mental health, as well as how they cope with the monumental task of keeping London safe and well.
During his visit, His Royal Highness said: "People are scared to talk about it, but they should be scared about not talking about it.
"'What you guys have to deal with every day, you don't know what you're going to get.
"It's strength to be able to talk about it."
His visit kicked off 2017's "Time to Talk Day" for the Heads Together charity campaign.
It aims to promote the sentiment that "conversations change lives" where mental health is concerned.
Heads Together is led by The Duke and Duchess of Cambridge and Prince Harry in partnership with eight leading mental health charities and three Founding Partners.
It has seen both Harry and the Duchess of Cambridge Kate Middleton visit charities and schools focusing on mental health.
In February 2016, Kate Middleton visited pupils at Salusbury School in Queens Park during Children's Mental Health Week to help raise awareness about mental health.
It has been a busy fortnight for the Royal, who also announced alongside Prince William that a memorial statue for their mother will be put up in Kensington Palace to mark 20 years since Princess Diana's death.
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