Bluebirds over the White Cliffs of Dover

Dame Vera Lynn's wartime classic is British, original, but not entirely without controversy. Ian Hislop discovers the chequered history of this musical mainstay of the British nation in its finest hour. Could it really be a song weighed down by politics, propaganda and even a touch of plagiarism? And what about those bluebirds - have you ever seen any in the Dover area? Ian meets Dame Vera Lynn, veterans, musicologists and even an ornithologist in his quest to find the hidden meaning of this classic wartime song.