In this edition, Derek visits two places which were shaped by the Industrial Revolution. In Powys, he is at the beautiful Lake Vyrnwy with fellow weather presenter Sian Lloyd. They learn about the village that was flooded to make way for the reservoir which still supplies Liverpool with water, and marvel at the famous dam, a Victorian engineering feat. In Tredegar, Derek goes on a trail back in time, discovering the rich history of this unique valleys town. He visits the largest lump of coal in the world, learns about a scheme that inspired the creation of the NHS and views the impressive remains of Sirhowy ironwork furnaces.