Across the east end of the nave of Canterbury Cathedral, where I was a volunteer guide for over a decade, there is a stone strainer arch erected by Prior Thomas Goldstone 500 years ago. It is a kind of tiebar, one of six which bind together the columns that support Bell Harry Tower, the cathedral’s dominant feature. The arch is essential to the integrity of the building’s central structure and is decorated with flowered designs and an inscription. On either side of the Prior’s initials and his rebus – three golden pebbles, a visual pun on his surname – there is the first verse of the psalm that begins Non nobis Domine (‘Not unto us, O Lord, but unto thy name give glory . . .’).