THE FIRST WORLD War was Britain’s September 11. Nothing comparable had happened to the British before and it changed the way they saw themselves and their security. For the first time since Dutch ships had sailed up the Medway in the seventeenth century, the homeland came under direct attack when Scarborough was shelled and London bombed. Almost every family suffered the death or wounding of at least one of its members. In south-eastern England, the sound of artillery echoed across the Channel as a distant reminder of the war’s most bloody aspect: the battles on the Western Front, its long, snaking line familiar now from several dozen television documentaries, each one accompanied by a suitably sepulchral commentary.