The Sir Ralph Abercromby is the only structure remaining in St Peter's Field after cavalry charged into a crowd had gathered to demand the reform of what? 
Sir Ralph Abercromby (pub): The Sir Ralph Abercromby, also known as the Abercrombie, is a pub in Manchester. Sir Ralph Abercromby (pub):  Originally built in the 19th century, it is the only structure remaining in St Peter's Field from the time of the Peterloo Massacre. Peterloo Massacre: The Peterloo Massacre occurred at St Peter's Field, Manchester, England, on 16 August 1819, when cavalry charged into a crowd of 60,000–80,000 who had gathered to demand the reform of parliamentary representation.
parliamentary representation