|Dr Allan Chapman introduces us to Newton, one of Britain's most influential scientists. Although born back in the difficult and violent times of the 1600's, Newton's ideas and discoveries still endure today. Through his key work 'Principia Mathematica' he gave us his theory on the Universal Laws of Motion - a work that gave us the terms 'action', 'reaction', 'inertia' and 'force'. Key to it, his most well-known discovery - thanks to a windfall apple - the theory of gravity. But Newton was also an inventor and Chapman talks us through some of his other, lesser-known creations like the world's first cat flap.