Kate Middleton shows off her new hairstyle as she joins William and Harry at charity event

Prince William, Prince Harry, and Catherine, Duchess of Cambridge are set to outline the next phase of their Heads Together campaign.

The three royals spearhead the charity - which aims to end the stigma around mental health and change the way it is talked about in national conversation - and are reportedly set to outline their plans for the campaign at an event in central London on Tuesday.

According to the Daily Express newspaper, the Duke and Duchess of Cambridge, 34 and 35 respectively, and Prince Harry, 32, will also meet with leaders from the world of media, technology, and business in the hopes of getting them to become supporters of their project.

During the event, the trio are expected to meet guests and give short speeches which will set out their expectations for the next year of Heads Together campaigning.

This year, Heads Together has been named as the charity of the year for 2017 London Marathon, and the campaign believes the honour is the "perfect springboard" to take them closer to their goal.

Writing on their website, the charity said: "Being the 2017 Virgin Money London Marathon Charity of the Year is the perfect springboard for the Heads Together campaign.

"We cannot wait to see hundreds of runners hitting the streets of London in April to end the stigma and change the conversation on mental health once and for all."

Pics: Getty Images

During the charity's last major event - which took place in October - the royals marked World Mental Health Day by pleading for society to recognise that psychological problems are suffered by people from many different walks of life.

Meanwhile, it was recently revealed that Prince William is set to give up his job as a helicopter pilot for the Air Ambulance service in order to focus more time on issues such as tackling homelessness and raising awareness about mental health issues.

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