Melvyn Bragg and his guests discuss Hadrian's Wall.
Clare Balding walks near Hay-on-Wye with a group who met while horse-trekking in Mongolia.
Clare Balding walks the final stage of St Oswald's Way.
Clare walks from the Severn Estuary to Brockweir, taking in Chepstow and Tintern Abbey.
Melvyn Bragg and guests discuss The Great Wall of China.