Set in stone: flint flushwork is a decorative art-form built into the fabric of medieval churches, and has survived where other artistry has not. Stephen Hart, in his Flint Flush-work: A medieval masonry art, which is illustrated with his own photos (left is the side wall of the porch at Chelmsford Cathedral), wants to see wider appreciation of this branch of church art (Boydell Press, £30 (£27); 978-1-84383-369-7)