Michael Portillo reaches Devon's county town, Exeter, dominated since the Middle Ages by its magnificent gothic cathedral. Michael joins the stonemasons charged with conserving the intricate medieval Beer stonework.From the top of the cathedral roof with its panoramic views, Michael descends around five metres below street level to explore a 425-metre network of tunnels known as the Exeter Passages. Back in the cathedral library, Michael inspects one of the oldest surviving anthologies of English poetry in the world, the Exeter Book, written around 1,000 years ago.Plymouth is Michael's last stop on this leg. The city has a rich maritime and military history, is home to the largest naval base in western Europe, and is a world-leading centre for marine engineering.