I n the decades after Coventry cathedral was destroyed by the Luftwaffe in 1940, the shattered fragments of what had once been its glorious medieval stained glass windows were packed into 30 wooden crates and stored in a cellar.

First smashed during the Reformation and then dismantled for safekeeping before the second world war, the cathedral authorities knew the remnants made up a treasure trove of spectacular 15th-century glass, but not, exactly, what had survived five turbulent centuries.

Thousands of stained-glass fragments have been brought together for the first time in over a decade, making this important collectionaccessible for visitors and researchers.…