In Rupert Brooke’s best-known poem, a soldier says that if he dies, there will be "some corner of a foreign field/That is for ever England." As I discovered nearly 30 years ago, such corners, dating from 1918 and 1919, can be found in a cemetery in Archangel (Archangelsk) in Russia’s far north. In her latest book, British journalist and historian Anna Reid explains how they came to be there.