David Walliams left his fans heartbroken on Tuesday after sharing an incredible photo of his great-grandfather John Boorman.MORE: Remembering the Britain's Got Talent stars who have sadly passed awayThe BGT judge's team, who run his Instagram account, posted a series of old black-and-white photos alongside the caption: "David’s great grandfather John Boorman who was a Grenadier Guard during the First World War.