Alan Yentob celebrates the 70th anniversary of the world's first scheduled high-definition television service, by the BBC from Alexandra Palace in 1936. He take some of the pioneering engineers and on-screen talent back to the studios to see what they can remember of TV's early days - from Picture Page to Muffin the Mule to the first news programme and the potter's wheel 'interlude'. Plus, some amazing archive footage and the Queen's 1953 coronation, the event that single-handedly changed how people viewed the fledgling TV service.