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 Captain Hugh Hornby Birley, a local factory owner, arrived at the house from where the magistrates were watching; some reports allege that they were drunk. Andrews, the Chief Constable, instructed Birley that he had an arrest warrant which he needed assistance to execute. Birley was asked to take his cavalry to the hustings to allow the speakers to be removed; it was by then about 1:40 pm. The route towards the hustings between the special constables was narrow, and as the inexperienced horses were thrust further and further into the crowd they reared and plunged as people tried to get