Cavalry charged a crowd demanding the right to vote, and killed at least 18

Sixty thousand people gathered peacefully in Manchester in 1819 to demand parliamentary representation. Local magistrates sent armed cavalry into the packed crowd to arrest a speaker, and the resulting crush and sabre charge killed at least 18 people and injured hundreds. The massacre was nicknamed 'Peterloo,' a bitter echo of Waterloo, and became a founding grievance behind Britain's later electoral reforms.

— Robert Poole, Peterloo: The English Uprising — 2019
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