Prince William, Duke of Cambridge, speaks with Emma Watson at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP
Prince William, Duke of Cambridge, speaks with Emma Watson at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP
Model Jessica Michibata arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Model Jessica Michibata arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Ralph Lauren and Ricky Anne Loew-Beer arrive for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Ralph Lauren and Ricky Anne Loew-Beer arrive for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actress Zhang Ziyi arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actress Zhang Ziyi arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actor Benedict Cumberbatch arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actor Benedict Cumberbatch arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Model Kate Moss arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Model Kate Moss arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actress Emma Watson arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actress Emma Watson arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Model Cara Delavigne arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Model Cara Delavigne arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actress Helena Bonham-Carter arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actress Helena Bonham-Carter arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actress Cate Blanchett arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
Actress Cate Blanchett arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle. Photo: Chris Jackson/Reuters
The Duke of Cambridge, left, speaks with Benedict Cumberbatch at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP
The Duke of Cambridge, left, speaks with Benedict Cumberbatch at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP
Prince William, Duke of Cambridge, left, speaks with Ralph Lauren at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP
Prince William, Duke of Cambridge, left, speaks with Ralph Lauren at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP
From left: Paul Arrouet, Dylan Lauren, Ralph Lauren, Ricky Anne Loew-Beer, Andrew Lauren, Lauren Bush and David Lauren pose at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP
From left: Paul Arrouet, Dylan Lauren, Ralph Lauren, Ricky Anne Loew-Beer, Andrew Lauren, Lauren Bush and David Lauren pose at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP
Prince William, Duke of Cambridge, left, speaks with Cate Blanchett at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP
Prince William, Duke of Cambridge, left, speaks with Cate Blanchett at a dinner to celebrate the work of The Royal Marsden at Windsor Castle. Photo: Doug Seeburg/AP

Prince William opened the doors of Windsor Castle to host a star-studded gala dinner to celebrate the work of The Royal Marsden Hospital.