Following his mother's death, Charles Drazin discovered a battered suitcase in his loft bearing the initials of his grandfather, a man he never knew. Inside was a treasure trove of photographs - of five men, in various far-flung locations. Following the most delicate of threads, he returned to the tiny village in Ireland where his mother was born, and began a search for the lives behind the images.

Mapping Empire is the result. It is the story of five brothers from rural Ireland, who travelled around the world as officers in the Royal Engineer Corps -surveying, exploring,...