Prince William and Lady Gaga have teamed up to talk about mental health - just a day after Prince Harry spoke of almost suffering a breakdown.

Around 15,000 people tuned in to a Facebook live where the Duke of Cambridge and pop star encouraged people to open up about their emotions.

In the video, posted by the royal family, the pair discussed bringing an end to the "shame" attached to mental health issues.

Lady Gaga also spoke of the 'life-changing' impact post-traumatic stress had had upon her life.

In a separate interview, William urged people to lose the British "stiff upper lip" culture - stressing the importance of speaking freely about such matters.

And in the same sit-down, younger brother Prince Harry revealed he almost suffered a mental breakdown by bottling up feelings over his mother's death for two decades.

Speaking from Kensington Palace to Lady Gaga in her Hollywood home, William stressed the importance of smashing the stigma around talking about mental health.

"It's time that everyone speaks up and really feels very normal about mental health, it's the same as physical health," he said.

"Everybody has mental health and we shouldn't be ashamed of it and just having a conversation with a friend or family member can really make such a difference."

He said many of the issues he had seen from his work with veterans, homelessness and addiction charities stemmed from mental health issues.

And the prince also praised the Poker Face singer for her bravery in revealing that she lives with post-traumatic stress disorder.

Lady Gaga said the diagnosis had had 'life-changing' effects on her life.

"For me, waking up every day and feeling sad and going on stage is something that is very hard to describe," she said.

"There is a lot of shame attached to mental illness, you feel like something's wrong with you.

"In my life I go, 'oh my goodness, look at all these beautiful, wonderful things that I have, I should be so happy', but you can't help it if in the morning when you wake up you are so tired, you are so sad, you are so full of anxiety and the shakes that you can barely think.

"It was like saying, 'this is a part of me and that's OK'."

She added that talking more openly about mental health would allow people dealing with it to feel like "we are not hiding any more".

Princes William and Harry have been increasingly vocal about openness around mental health and have championed the Heads Together campaign.