According to wikipedia(albeit i admit, the article doesnt state a source for this information) Corfe Castle fell due to an inside betrayal after being besieged for only 2 months
During the English Civil War, the castle twice came under siege by Parliamentarian forces. Sir John Bankes was away from his estate attending to Charles I so defence of the castle was led by his wife Lady Mary Bankes — "Brave Dame Mary" as she became known.

The first siege, in 1643, lasted for six weeks before the Parliamentarians withdrew with the loss of 100 men. The second siege, in 1646, was resisted for two months before the castle was betrayed by a member of the garrison.
http://en.wikipedia.org/wiki/Corfe_Castle

Dunno though, according to the article about the lady herself it says
However, because she showed such courage she was allowed to keep the keys of the castle, which are now held at Kingston Lacy near Wimborne, Dorset.
(this article also states that it was an inside job though) so there at least seems to have been fighting going on :P