on Wales and _the March during
the Barons' Wars_ in _Owens College Historical Essays_, pp.
76-136 (1902).

The change of policy of the marchers was partly at least brought about
by their constant difficulties with the Prince of Wales. During the
period immediately succeeding the Provisions of Oxford, Llewelyn ceased
to devastate the marches. A series of truces was arranged which, if
seldom well kept, at least avoided war on a grand scale. Within Wales
Llewelyn fully availed himself of the respite from English war.
Triumphant over the minor chiefs, he could reckon upon the support of
every Welsh tenant of a marcher lord, and at last grew strong enough to
disregard the truces and wage open war against the marchers. It was in
vain that Edward, the greatest of the marcher lords, persuaded David,
the Welsh prince's brother, to rise in revolt against him. Llewelyn
devastated the four cantreds to the gates of Chester, and at last,
after long sieges, forced the war-worn defenders of Deganwy and Diserth
to surrender the two strong castles through which alone Edward had
retained some hold over his Welsh lands. It was the same in the middle
march, where Llewelyn turned his arms against the Mortimers, and robbed
them of their castles. Even in the south the lord of Gwynedd carried
everything before him. "If the Welsh are not stopped," wrote a southern
marcher, "they will destroy all the lands of the king as far as the
Severn and the Wye, and they ask for nothing less than the whole of
Gwent." Up to this point the war had been a war of Welsh against
English, but Montfort sought compensation for his losses in England by
establishing relations with the Welsh. The alliance between Montfort
and their enemy had a large share in bringing about the secession of
the marchers. Their alliance with Edward neutralised the action of
Montfort, and once more enabled Henry to repudiate the Provisions.

In the summer of 1263, Edward and Montfort both raised armies.
Leicester made himself master of Hereford, Gloucester, and Bristol, and
when Edward threw himself into Windsor Castle, he occupied Isleworth,
hoping to cut his enemy off from London, where the king and queen had
taken refuge in the Tower. But the hostility of the Londoners made the
Tower an uneasy refuge for them. On one occasion, when the queen
attempted to make her way up the Thames in the hope of joining her son
at Windsor, the citizens assailed her barge so fiercely from Londo