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According to the Brut Chronicler, Bishop Burgesch forgot his ecclesiastical dignity completely. He made a bid to flee by running to the lavatory and trying to throw himself down the chute that evacuated human waste to the moat outside.
Oh, the drama ;)
Going down the lavatory chute might have been the sensible thing to do in his situation, though, being deemed as a traitor to the true king and facing a horrible death.
Stories like this make this book an incredibly fun and entertaining read.