Flatford Lock was one of thirteen locks placed along the River Stour to assist the passage of barges up and down the river. Constable’s father, Golding Constable, was one of the Commissioners of the River Stour Navigation, who were responsible for keeping the locks in order.

Constable knew this subject well, and painted it often. In this sketch he depicted Flatford Lock from the millpool end, beneath the trees that appear at the right of Flatford Mill from a lock on the Stour    painted at around the same time, with Flatford Bridge and Bridge Cottage in the distance. He showed the timber-framed lock chamber with the many beams spaced along it.

Constable wrote that ‘the sound of water escaping from Mill dams … Willows, Old rotten Banks, slimy posts, & brickwork. I love such things … As long as I do paint I shall never cease to paint such Places’ (Beckett VI, p. 77).