"killing stone" = 400

400 = Buckingham Palace

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Marine Corps Infantry Veteran 0351, Jesus is Lord, Q, Tacos & Tequila, America The Free.

The 1665–66 epidemic was on a much smaller scale than the earlier Black Death pandemic. It became known afterwards as the "great" plague mainly because it was the last widespread outbreak of bubonic plague in England during the 400-year Second Pandemic

https://en.wikipedia.org/wiki/Great_Plague_of_London