The eco-group revealed Hayley Walsh, 42, and Richard Weir, 60, were behind the stunt which took place at the Theatre Royal in London 's Covent Garden last night.
Think you know all of the Monarchs off by heart? Prove it with this tricky quiz. In the mood for more historical sing-alongs? Catch up on series 10 of Horrible Histories on BBC iPlayer now.
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