At Whitsuntide the barons met Simon at Oxford and finally summoned Henry to observe the Provisions.
His refusal was met by an appeal to arms.

Throughout the country the younger nobles flocked to Simon's standard, and the young Earl of Gloucester, Gilbert of Clare, became his warmest supporter.

His rapid movements foiled all opposition.

While Henry vainly strove to raise money and men, Simon swept the Welsh border, marched through Reading on Dover, and finally appeared before London.
[Sidenote: Mise of Amiens] The Earl's triumph was complete.

Edward after a brief attempt at resistance was forced to surrender Windsor and disband his foreign troops.