At 92, Dame Vera Lynn is still merrily doing her bit for Britain – and pulling off a mean impression of Marlene Dietrich. To mark the publication of her latest memoir, she talks (and sings) to Nigel Farndale The woman who answers the door has a face at once strange and familiar. She looks like Dame Vera Lynn, only how she would have looked about 30 years ago. It is more a trick of the genes than the light. 'I'm Vera's daughter,' she says in a voice similar to her mother's, with its faint traces of the East End....