Donor Henri de Werl, protected by St. John the Baptist

The Werl Triptych wing showing the donor Henri de Werl protected by Saint John the Baptist represents one of the most accomplished integration of donor portraiture with sacred narrative in fifteenth-century Flemish painting. De Werl, a Cologne theologian, is shown kneeling in prayer within the same space as his holy patron — a spatial convention that asserts the immediate accessibility of the divine to the devout layperson. Campin's handling of the reflective convex mirror in the background, which reveals the room extending behind the viewer, is one of the most technically dazzling moments in early Flemish painting, demonstrating his mastery of light reflection equal to anything achieved by Jan van Eyck.

The panel features Campin's characteristic convex mirror reflecting the room's interior, a virtuoso detail alongside the meticulous rendering of the donor's features, the saint's lamb, and the tiled floor rendered in careful perspective.