‘The popular belief that British troops suffered horrific casualties as a result of the German use of mustard gas is a myth,’ he says. ‘We have all seen pictures of lines of men with bandages on their eyes, shuffling along, hand on shoulder of man in front and everyone thinks they have been blinded by gas. But what mustard gas did was cause conjunctivitis and temporary blindness. The British and the French, in order to make the Germans look more beastly, exaggerated its impact.’