In the Welsh mountains of Snowdonia, Michael Portillo reaches an abandoned mine, where in 1940 the wartime government sought sanctuary for the National Gallery’s priceless art collection. Michael hears how, as invasion appeared imminent, great masterpieces were transported by train and lorry to be stored hundreds of feet beneath the ground in a natural granite bunker.

At Tan y Bwlch, Michael meets 'Blanche', who used to haul slate at Penrhyn quarry and was built in 1893. Now beautifully restored, she takes Michael on a memorable ride on the oldest narrow-gauge line in the world, the Ffestiniog Railway.

In the harbour town of Porthmadog, Michael investigates the Welsh origins of a man forever associated with the Middle East, Lawrence of Arabia.