On the whole, Buckinghamshire took the Parliament's side in the Civil War. Ayesbury, 14 miles from Brill, was occupied by Parliamentery troops from 1642 onwards. Oxfordshire, on the other hand, was emphatically a Royalist county. Brill, only 12 miles from Oxford, was therefore the centre of a sort of no-man's land and, as such, the village was coveted by both sides.
The Battle of Edgehill in November 1642 was fought less than 30 miles from Brill. After the battle, Charles I withdrew to Oxford and, in the December of that year, a royalist force under the command of Sir Gilbert Gerard was sent to occupy Brill. The next month Parliamentary troops led by Arthur Goodwin determined to dislodge the Royalists, and the 'Battle of Brill' was fought on Friday January 27th 1643.
A report of the time describes Brill as:
"a Towne fortified by nature, standing upon a hill, and made stronger by art, having out-works...the like not to be found in any Towne in England."
It would seem that the Royalists had been busy since their arrival converting the old castle earthworks into a complicated series of ramparts and ditches.
These structures stood up well to the cannonade from the Roundhead force, and the assault continued off and on for two hours. The Royalists finally set fire to some damp straw, which made so much smoke that the Parliamentarians decided to abandon the attack.
We do not know how many men were killed or wounded in the Battle of Brill. Roundhead sources suggest 10 fatalities, whilst Royalist reports (probably in exaggeration) say about 80 men were killed and 40-50 wounded.
It was not until the winter of 1644-45 that Brill was finally occupied by Parliamentary forces with 1,000 infantry. Oxford surrendered on June 24th 1646, and with the city's fall the Civil War was, to all intents and purposes, over.
There are few reminders of England's Civil War in Brill. Burial records for 1643 suggest that some, if not all, of the men killed in the Battle of Brill are buried here, and the remains of the Royalist fortifications can probably still be seen on the northern hillside. The earthworks between the Thame and the Oakley roads may date from the time of Brill's final conflict in 1644-45.