Riot Act felt uncertain of their power to take action to stop the riots without a reading of the Riot Act. After the riots, Lord Mansfield observed that the Riot Act did not take away the pre-existing power of the authorities to use force to stop a violent riot; it only created the additional offence of failing to disperse after a reading of the Riot Act. The Riot Act was read prior to the Peterloo Massacre of 1819, as well as prior to the Bristol Riots at Queen's Square in 1831. Both are held to be related to the Unreformed House of
Peterloo Massacre for parliamentary reform, organised a demonstration to be addressed by the well-known radical orator Henry Hunt. Shortly after the meeting began, local magistrates called on the Manchester and Salford Yeomanry to arrest Hunt and several others on the hustings with him. The Yeomanry charged into the crowd, knocking down a woman and killing a child, and finally apprehending Hunt. The 15th Hussars were then summoned by the magistrate, Mr Hulton, to disperse the crowd. They charged with sabres drawn, and in the ensuing confusion, 15 people were killed and 400–700 were injured. The massacre was given the name Peterloo in