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 many as 150,000; modern estimates are 60,000–80,000. Scholar Joyce Marlow describes the event as "The most numerous meeting that ever took place in Great Britain" and elaborates that the generally accepted figure of 60,000 would have been six per cent of the population of Lancashire, or half the population of the immediate area around Manchester. Although some observers, like the Rev. W. R. Hay, chairman of the Salford Quarter Sessions, claimed that "The active part of the meeting may be said to have come in wholly from the country", others such as John Shuttleworth, a local cotton manufacturer, estimated that