Pam Ayres travels beyond the Cotswolds borders at Highclere Castle, one of Britain's most recognisable stately homes and now better known as Downton Abbey. As well as exploring some rooms that will be familiar to millions of TV viewers, she finds out more about Highclere's fantastic gardens, designed by Capability Brown, and learns about Highclere's involvement in the discovery of Tutankhamun's tomb in Egypt 100 years ago