There are several baptisms of Ann Cannon around the right time but the most likely would seem to be one at St Leonard Shoreditch (where she married in 1817) in 1790 but one would need further evidence to be reasonably certain. The parents for this baptism are shown as James and Mary. However, the only marriage of a James Cannon to Mary that I could find was in 1792 at St Mary Lambeth. There is a marriage in 1785 of James Cannon to Ann Grace Huntley at St Leonard Shoreditch; for this to be the right marriage the baptism entry should have shown the mother as Ann and not Mary.