Jon Cannon was my PhD buddy at The University of Bristol and then became a friend. His impressive knowledge of English cathedrals and parish churches sprang from an encounter with the tiny church of St Michael atop the rocky outcrop of Brentor in Devon in January 1974 when he was 11 years old, recently moved to the English west country from London, and out exploring with his mother. He described it as follows: ‘It was as if someone took a giant key, put it in a keyhole in my heart that I didn’t even know existed, and turned it.’ This event was his call to vocation, and he devoted his life to studying, writing, and communicating about sacred places, especially medieval religious architecture in England, resulting in Cathedral: The Great English Cathedrals and the World that Made Them (London: Constable, 2007) and other books. The Dean of Westminster, David Hoyle, who was at one time Dean of Bristol Cathedral, described Jon as ‘a long man’, and affectionately noted how ‘Jon’s suits always seemed to have a secret life of their own, they looked as though they might have the odd adventure of their own when he wasn’t looking.’ Jon was passionate and interested in everything. This sketch was made when we visited him and his family just after Christmas 2022 and 6 months before he died, far too soon at the age of nearly 61 on 4 May 2023, still passionate and engaged with life, and not yet finished. It was my honour to do a last-draft edit of his book, Stones of Britain: Geology and history in the British Landscape to be published by Constable in 2025.  His attribute is Brentor, the catalyst that called him to his life’s work.