When the Chartist petition with 1,283,000 signatures was rejected by Parliament in summer 1839, tension grew, culminating in the Newport Rising. O'Connor was not involved in the planning of this event, though he must have known that there was a mood for rebellion among Chartists. He was a dangerous man to the authorities, and a sentence of 18 months in York Castle was passed on him in May 1840. In his farewell message, he made clear what he had done for the movement: