Rudolf Rassendyll (as a King ) didn't allow Duke Michael to enter the room at Flavia's house on purpose.

On purpose ------by mistake

Rudolf Rassendyll (as a King ) didn't allow Duke Michael to enter the room at Flavia's house as he didn't know the rules

So he hoped Fritz had told him
He used to make mistakes as he wasn't a king and knew nothing about rules except what Sapt taught him

didn't permit

on purpose=by mistake

on purpose> by mistake / as he didn't know the rules/ by accident

on purpose - unintentionally

on purpose - accidently

on purpose by mistake or accidentally