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LONDON, ENGLAND - JANUARY 17: Catherine, Duchess Of Cambridge adjusts marathon runner Jon Salmon's headband as Prince William, Duke of Cambridge (L) and Steve Jackson look on during an event to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Stefan Wermuth - WPA Pool /Getty Images)

LONDON, ENGLAND - JANUARY 17: Catherine, Duchess Of Cambridge adjusts marathon runner Jon Salmon's headband as Prince William, Duke of Cambridge (L) and Steve Jackson look on during an event to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Stefan Wermuth - WPA Pool /Getty Images)
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LONDON, ENGLAND - JANUARY 17: (L-R) Prince William, Duke of Cambridge, Catherine, Duchess Of Cambridge, Prince Harry, Steve Jackson and marathon runner Jon Salmon during an event to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Stefan Wermuth - WPA Pool /Getty Images)

LONDON, ENGLAND - JANUARY 17: (L-R) Prince William, Duke of Cambridge, Catherine, Duchess Of Cambridge, Prince Harry, Steve Jackson and marathon runner Jon Salmon during an event to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Stefan Wermuth - WPA Pool /Getty Images)
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LONDON, ENGLAND - JANUARY 17: Catherine, Duchess Of Cambridge speaks during a briefing to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon as Prince William, Duke of Cambridge looks on at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Stefan Wermuth - WPA Pool /Getty Images)

LONDON, ENGLAND - JANUARY 17: Catherine, Duchess Of Cambridge speaks during a briefing to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon as Prince William, Duke of Cambridge looks on at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Stefan Wermuth - WPA Pool /Getty Images)
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LONDON, ENGLAND - JANUARY 17: Prince William, Duke of Cambridge and Catherine, Duchess Of Cambridge speak to guests during a briefing to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Stefan Wermuth - WPA Pool /Getty Images)

LONDON, ENGLAND - JANUARY 17: Prince William, Duke of Cambridge and Catherine, Duchess Of Cambridge speak to guests during a briefing to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Stefan Wermuth - WPA Pool /Getty Images)
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LONDON, ENGLAND - JANUARY 17: Catherine, Duchess of Cambridge, Prince William, Duke of Cambridge and Prince Harry attends a briefing to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Danny Martindale/WireImage)

LONDON, ENGLAND - JANUARY 17: Catherine, Duchess of Cambridge, Prince William, Duke of Cambridge and Prince Harry attends a briefing to announce plans for Heads Together ahead of the 2017 Virgin Money London Marathon at ICA on January 17, 2017 in London, England. Heads Together, Charity of the Year 2017, is led by The Duke & Duchess of Cambridge and Prince Harry in partnership with leading mental health charities. (Photo by Danny Martindale/WireImage)
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