LONDON (AP) — Working alone in a tiny office in London, Christian Lamb tried to make sure British troops were in exactly the right place when they scrambled onto Normandy’s beaches under enemy fire during the D-Day landings.

Referring to huge maps of the French coast on the wall in front of her, the young Women’s Royal Naval Service officer painstakingly created detailed maps to guide the crews of landing craft that ferried the men to shore.

The maps “showed railways, roads, churches, castles, every possible feature that could be visible to an incoming invader and from every angle,” Lamb, now 103, told The Associated Press. “It was intense and exciting work, and obviously detail was vital. It was crucial that the maps were 100% accurate.”