Elisha Trewartha is settling into the working day. He’s a “middle-aged man… the foreman” at Upton Towans Dynamite Works, Gwithian.

At first, it feels like an earthquake. Windows shatter in Penzance, and oscillation disturbs mid-morning visitors to St John’s Hall. At St Ives, shops lose their plate glass and roofs are damaged. The earth rumbles; a “dull, hollow boom” is in the air. But then the rumours start.....