The second in our series of portraits of figures from the history of North East England who challenged their age, recorded in front of audiences at Radio 3's Free Thinking festival at The Sage Gateshead in 2009. Henrietta Heald profiles the Victorian inventor, arms dealer and industrialist William Armstrong. Armstrong brought global fame to the Tyne, employing thousands in the manufacture of machinery, ships - and guns. But he also created the first house in the world to be lit by hydroelectricity. He epitomised the dynamism of his age and attracted many epithets, from "visionary genius" to "merchant of death".