Sir David Attenborough shares rare public message to mark 100th birthday Broadcaster and conservationist Sir David Attenborough is officially 100 years old – yet another thing he can add to his seemingly endless list of achievements. The Planet Earth presenter, who has been a British TV staple for 75 years, is celebrating becoming a centenarian with a live event on BBC One tonight , with a host of stars stopping by to deliver birthday messages to the man who put nature documentaries on the map. From his memorable gorilla encounter to meeting the late Queen Elizabeth II and taking to the Glastonbury stage, tonight’s live show will look back on Sir David’s career-making moments with special performances from Bastille’s Dan Smith, Icelandic band Sigur Rós , and British singer Sienna Spiro. Get your tissues ready as we prepare for what will undoubtedly be one of the most emotional TV events of the year. Who'll be performing at 'David Attenborough's 100 Years on Planet Earth'?…