Limestone from Caen, Normandy; much favoured by masons who found it easy to work – hence used extensively at the cathedral .
Local examples (click to enlarge)
Cromwellian House, Green Court to the north of the cathedral
Bell Harry Tower, cathedral – now a mix of original Caen stone and various restoration stones
Cathedral library rebuilt 1955 after WW2 damage - lower half of wall is re-used Caen stone