[1] The Fortifications of Portsmouth were so strong that after it was captured by Parliament and properly garrisoned, it was suggested by some that it would take as many as 40,000 men to seize it.

[2] Its governor at the time was George Goring who managed to convince both sides of his loyalty and as a result received funds from both the king and Parliament.

[12] On the night of 15 August, Parliamentarian forces under Captain Browne Bushell captured the Henrietta Marie in a cutting out operation.

[11] Meanwhile, the Parliamentarian forces began to prepare a firing position in Gosport under the direction of John Meldrum.

[13] On the night of 4 September, a Parliamentarian force of 400 infantry equipped with ladders and backed by cavalry set out to attack the castle.

[13] At around this time, the guns of Portsmouth once more opened fire on the assaulting force, and the Parliamentarians responded by scaling the walls and capturing the castle without further opposition.

[2] Under the terms of the agreement, the garrison was granted safe passage and all prisoners were released with the exception of Parliamentarian deserters.

[2] The Royalists were in part able to obtain such favourable terms due to the threat of detonating Portsmouth's gunpowder reserves, including 1,200 barrels stored in the Square Tower.

[15] A couple of days were allowed for Goring and the garrison to settle their affairs and Parliament came into formal possession of the town on 7 September at 06:00.