When the blitz began in September 1940, Londoners sought the safety of deep Underground stations and tunnels – and Henry Moore, the most famous British modern artist of the age, went down there to sketch them. His eerie drawings of people neatly lying in rows or sitting haggard in vortex-like ashen tunnels are startling and disorienting because they don’t bear any resemblance to our myths about the second world war. Where are the perky cockneys defying the Nazi bombs? These people burrowing into the earth to survive look desperate rather than indomitable. The works don’t even look very British: instead...