She decided to interrupt her journey by stopping at Leeds Castle which legally belonged to her as the fortress and its demesne were part of her dower to be retained in widowhood.

[12] Badlesmere, who by then had become disaffected with King Edward and had joined the swelling ranks of his opponents, was away at a meeting of the Contrariants in Oxford at the time and had left Margaret in charge of the castle.

[16] Margaret allegedly told Isabella's marshal, whom she met on the lowered drawbridge, that "the Queen must seek some other lodging, for I would not admit anyone within the castle without an order from my lord [Baron Badlesmere]".

[17] After issuing her message, she subsequently ordered her archers to loose their arrows upon Isabella from the battlements when the Queen (having ignored Margaret's communication) approached the outer barbican,[18][19] in an attempt to enter the castle by force.

[20] The unexpected, lethal volley of arrows, which killed six of the royal escort, compelled Isabella to make a hasty retreat from the castle and to seek alternative accommodation for the night.

Following a relentless assault of the fortress, which persisted for more than five days[n 2] and with the King's troops using ballistas, Margaret surrendered at curfew on 31 October having received a "promise of mercy" from Edward.

[24] Throughout the siege, she had expected the Earl of Lancaster to arrive with his soldiery to relieve her, but this he had refused to do;[23][n 3] nor had any of the other Contrariants or the Marcher Lords[n 4] come to her assistance, which left her to defend the castle with merely her husband's nephew, Bartholomew de Burghersh, and the garrison troops.

[23] Baron Badlesmere, although supportive of Margaret's conduct, had only managed to despatch some knights from Witney to augment the garrison troops in the defence of Leeds.

[15] Once King Edward had gained possession of the castle and the Badlesmere treasure within, the seneschal, Walter Colepepper and twelve of the garrison were hanged from the battlements.

[29] The first sparks to the uprising had been ignited when, prior to his expulsion, the rapacious Hugh le Despenser the Younger had persuaded the infatuated King to grant him lands in the Welsh Marches which rightfully belonged to entrenched Marcher barons such as Roger Mortimer,[30] his uncle Roger Mortimer de Chirk, and Humphrey de Bohun, 4th Earl of Hereford, a staunch Ordainer albeit the King's brother-in-law.

[n 7] They had formed a confederation and made devastating raids against Despenser holdings in Wales; and Mortimer led his men in an unsuccessful march on London.

These mutinous events, in addition to other incidents which created a tense situation and called for a mobilisation of forces throughout the realm, eventually led to the Ordainers constraining the King to exile the favourites.

However, subsequent to his capture of Leeds Castle and the harsh sentences he had meted out to the insubordinate Margaret de Clare and her garrison, King Edward defied the Contrariants by persuading the bishops to declare the Despensers' banishment illegal at a convocation of the clergy, and he summoned them home.

[25] As a result of Margaret's imprisonment, Badlesmere remained firmly aligned with the King's opponents; shortly afterwards he participated in the Earl of Lancaster's rebellion.

By this time Edward III had ascended the throne; however, the de facto rulers of England were Queen Isabella and her lover, Marcher Lord Roger Mortimer, 1st Earl of March (father-in-law of Margaret's daughter Elizabeth), who jointly held the Office of Regent for the new king.