The Essex Chapel (originally known as the Morison Chapel) can be seen in Saint Mary's today. Described by Pevsner as "the chief glory of Watford Church", the chapel is noted for its large, ornate wall monuments by the sculptor Nicholas Stone. On the south side is the memorial to Sir Charles Morison (d.1599), and opposite is another to his son and heir, Sir Charles Morrison, 1st Baronet (d.1628). Both are lavishly decorated and feature sculpted effigies of the deceased and their family members. Monuments to various Earls of Essex are mounted on the chapel walls.