On 6 November, while John Peckham, archbishop of Canterbury, was conducting peace negotiations, Edward's commander of Anglesey, Luke de Tany, decided to carry out a surprise attack.
Den 6. november, mens ærkebiskoppen af Canterbury, John Peckham, var i gang med fredsforhandlinger, besluttede Edvards kommandør i Anglesey, Luke de Tany, at udføre et overraskelsesangreb.