At the Big Pit Mining Museum in South Wales, Melvyn looks back to the 1930s and salutes Britain's Black Diamonds, brave miners who risked their lives digging for the coal that powered an Empire. Vicky Stradling tells the shocking truth about one of the worst disasters in coal mining history. Melvyn goes underground to learn about the limited safety equipment used by coalminers in the 1930s. And David Bogg reveals the occupational hazards of working with pit ponies.