Eighteen kilometres of pillboxes and tunnels the British cut across Hong Kong between 1936 and 1938, confident it would hold the Japanese advance for weeks. The tunnels were named after London landmarks so troops could navigate them, which is the detail that stays with you: a hillside in the New Territories, found your way around by the West End. Its keystone, the Shing Mun Redoubt, had room for 120 men and was garrisoned by 43. The line fell in two days.