The Duke of Cambridge has launched an ambitious charity appeal which aims to raise £100 million in aid of the Royal Marsden hospital.
In a specially made film William urged the public to help the Royal Marsden Cancer Charity reach its target over the next 10 years and fund the hospital's "amazing work".
The Royal Marsden is a world-leading cancer centre specialising in all areas of diagnosis, treatment, care and research into the disease.
The Duke has been its president since 2007 and in his message of support said: "I am extremely proud to be president of the Royal Marsden, an incredible hospital and a world-class cancer centre carrying out ground-breaking work influencing the treatment of cancer patients all over the UK."
William highlighted how he and wife Kate had visited, and opened, the Royal Marsden's cancer unit for children and young people at its hospital in Sutton, south London.
As images were shown of the royals during their trip to the centre in September 2011, the Duke explained how young cancer patients were treated in a state-of-the-art environment.
William wore a suit, shirt and tie in the film which has been posted on YouTube today.
He added: "In 2013 The Royal Marsden Cancer Charity is celebrating a decade of innovation, looking back at 10 years of pioneering developments they have funded, and looking forward to the next 10 years of innovation and personalised treatment. The charity needs to raise £100 million if they are to make this a reality. This year please help the Royal Marsden to continue their amazing work as a centre of innovation and help make a difference for people with cancer everywhere."
Tottenham striker Jermain Defoe will visit the Royal Marsden's hospital in Sutton to attend a launch event for the fundraising campaign. The footballer's father died at the south London hospital last year following a battle against cancer.
Cally Palmer, the Royal Marsden's chief executive, said she was delighted that the Duke of Cambridge agreed to take part in the film. She added: "The Royal Marsden Cancer Charity plays a vital role in ensuring the Royal Marsden stays at the forefront of cancer research, diagnosis, treatment and care and we are extremely fortunate to have a president who is so involved and interested in everything we do from the latest technology to the care and wellbeing of patients and their families."