The enemy now decided to starve out Lady Bankes, and threatened to kill anyone caught conveying food to the castle. This measure was effective, for Lady Bankes, being without sufficient food and ammunition to withstand a siege, agreed to deliver up the guns, on the condition that she should remain in possession of the castle unmolested.
Lady Bankes had, however, little confidence in the honour of the attacking party, and felt assured that they would before long, in spite of their promise, endeavour to take possession of the castle. This was made evident by the behaviour of the soldiers, who, although they did not enter the castle, did not hesitate to boast that it belonged to them, and that they would take possession of it whenever it was required. But Lady Bankes was determined that it should not, if she could possibly prevent it, fall into the hands of the enemy. Therefore she gave instructions that the men appointed to watch the castle should be supplied liberally with food and drink, with the result that they neglected to do their duty, and allowed Lady Bankes to smuggle in sufficient provisions and ammunition to withstand a long siege. Moreover, Lady Bankes despatched a messenger to Prince Maurice, asking him to send a force to help her hold the castle against the enemy, and in reply to her appeal Captain Lawrence and some eighty men arrived upon the scene.
The Parliamentarians had now become aware of the fact that Lady Bankes was taking steps to render the castle capable of withstanding a siege, and they decided to occupy it at once.
On June 23, 1643, Sir Walter Earle arrived before the castle with a force of about 600 men, and called upon Lady Bankes to surrender, which she firmly but courteously declined to do. Her refusal greatly incensed the besiegers, who thereupon took an oath that 'if they found the defendants obstinate not to yield, they would maintain the siege to victory, and then deny quarter unto all, killing without mercy men, women and children.'
The Parliamentarians, possessing several pieces of ordnance, opened fire on the castle from all quarters, but did comparatively little damage, and their attempts to carry it by assault were equally unsuccessful.
When some days had passed, and the attacking forces were no nearer capturing the castle than when they first arrived, the Earl of Warwick sent to their assistance 150 sailors, a large supply of ammunition and numerous scaling-ladders. Possessing these ladders, the Roundheads anticipated that the castle would soon be in their hands. They divided their force into two parties, one assaulting the middle ward, which was defended by Captain Lawrence, and the other, the upper ward, where Lady Bankes, her daughters, women-servants and five soldiers were the sole defenders.
As the Parliamentarians fixed their ladders against the castle wall Lady Bankes and her brave assistants showered down upon them red-hot stones and flaming wood. The soldiers too, delighted at the bravery of the mistress of the castle, fought desperately, and not one of the enemy succeeded in gaining entrance to the castle.
Sir Walter Earle, seeing that he could not carry the castle by assault, withdrew with a loss of one hundred killed and wounded. He would in all probability have made another attack, but during the evening the news reached him that the king's forces were approaching, and overcome by fear he ordered a retreat, leaving behind muskets, ammunition and guns, all of which fell into the hands of Lady Bankes and her gallant garrison.
After this siege, which had lasted for six weeks, Lady Bankes was allowed to remain for two years in undisturbed possession of the castle; but she lived in the knowledge that at any time another attempt to capture it might be made, as it was the only place of any importance between Exeter and London that remained loyal to the royal cause. Threats were constantly reaching her from certain members of the Parliamentary party, and to add to her trials her husband, whom she had not seen for two years, died at Oxford on December 28, 1644.
In October, 1645, the Parliamentary army decided to make another and more determined effort to capture Corfe Castle, and a large force was sent to besiege it. Lady Bankes and her handful of men had now pitted against them some of the best regiments in the victorious Parliamentarian army, but they scorned to surrender to them.