Prince Edward has spoken out about the King’s health ahead of the duke’s landmark birthday on Sunday. The Duke of Edinburgh thanked the public for the “extraordinary support” following his brother’s cancer diagnosis in February. Prince Edward is set to celebrate his 60th birthday on Sunday after a week of public engagements with his wife Sophie, Duchess of Edinburgh. The late Queen Elizabeth II’s youngest child said: “We were all hugely grateful for the extraordinary support from everyone. “I know he has been very touched by it all.” The King has been undergoing treatment for an undisclosed fo…