Julia begins her exploration of Britain's lost rail empire in Derbyshire, the heart of the Peak District, with a walk along the popular Monsal Trail. Limestone cliffs and gorges abound, not to mention the tunnels and soaring viaducts of the Midland Railway - one of the most dramatic and unlikely main lines ever built.

Julia walks along the stunning Mawddach estuary in north Wales. The area between Dolgellau and the coastal resort of Barmouth is one of the least visited parts of Snowdonia, but in the 1860s it received a great rush of holidaymakers, taking advantage of the new railway that connected the valley to the cities of England.

Tin and copper once made the area around Redruth the richest patch of land in the country. They inspired great engineering feats and pioneering tramways, the forebears of the rail empire. Julia Bradbury has her work cut out as she crosses an entire county, winding past Cornwall's crumbling engine houses and following a railway that has not operated for 140 years.