During the morning of 12 November the royal army assembled on Hounslow Heath expecting to encounter parliamentary forces.  Finding none, Prince Rupert intended to take command of the troops for the assault on Brentford, but General Patrick Ruthven Earl of Forth, a 69 year old officer with long military experience in Swedish service who would be made Earl of Brentford in 1644, came up and took overall control of royalist forces whilst Rupert retained command of the horse. Ruthven had been appointed Lord General of the royalist army after the death of the Earl of Lindsey at Edgehill and, in terms of the established chain of command, was Rupert’s superior.

The royalist attack appears to have been made by cavalry to the west of Brentford along the London Road.  Given that the royal army had to march from various locations west of London and assemble on Hounslow Heath before commencing the advance on Brentford, it seems unlikely that the attack commenced much before midday, a view supported by contemporary sources.  Many accounts of the battle make reference to the heavy mist over Brentford that day which helped the royalists achieve tactical surprise. 

Sir Richard Bulstrode, serving in the Prince of Wales’ regiment of horse, noted that his regiment was forced to retreat after being surprised by parliamentary artillery placed behind a great hedge and had to await the arrival of the royalist foot before pressing the attack.  This is likely to have been in the vicinity of Sir Richard Wynn’s house, west of Brentford End, as John Gwyn, a soldier serving in Sir Thomas Salisbury’s Welsh regiment of foot, indicated that the first parliamentary forces (almost certainly of Denzil Hollis’ red coated regiment of “butchers and dyers“) were engaged by the royalists at Wynn’s house, as well as along the Thames, presumably in the vicinity of Syon House.  Just before his regiment went into battle, Sir Thomas is said to have told his men “gentlemen, you lost your honour at Edgehill, I hope you will regain it here“.  

The parliamentary pickets at Wynn’s House were cleared and the royalists advanced to find the entrance to New Brentford blocked by a small barricade at the bridge across the River Brent.  A further royalist attack, with overwhelming numbers - one royalist account talks of 1,000 musketeers,  dislodged the parliamentary troops in under one hour and forced them to retreat from this defensive position to another “work”, probably a barricade, between New and Old Brentford, and join Lord Brooke’s regiment of foot.

The approaches to this new position were covered by a brick house and by two small pieces of artillery and the barricade was likely to have been positioned at the top of the ground that rises eastward through the western end of Old Brentford.  The royalist forces seem to have had some difficulty in overcoming this obstacle.  A royalist soldier writing a few days after the battle noted that “my Colonel’s (Sir Edward Fitton) regiment was the sixth that was brought up to assault, after five others had all discharged, whose happy honour it was (assisted by God, and a new piece of cannon newly come up) to drive them from that worke too“.  Gwyn also implies the fighting was hard throughout the battle when describing royalists tactics as “after once firing suddenly to advance up to push of pikes and the butt end of muskets“.

Parliamentary troops driven from this position are said to have been routed; some through Old Brentford toward London but others into the River Thames with a significant number drowning, though probably less than the two hundred claimed in one royalist account.  The parliamentary troops forced into the Thames must have been prevented from retreating toward London by royalist forces that had either worked around the right flank of the parliamentary defensive position through the enclosure and houses - making the barricade position untenable, or by a sudden  breakthrough, exploited by the royalists with speed, that forced the parliamentarians defending the left flank anchored on the river to surrender or swim.

The royalists continued their advance through Old Brentford only to encounter fresh parliamentary troops in an open field outside the town, possibly as far as Turnham Green.  These were the green coats of John Hampden’s regiment of foot, which were said, unsourced, by one nineteenth century historian to have come from Uxbridge, but are more likely to have advanced from Acton. According to one parliamentary news sheet, Hampden’s troops charged the royalist forces five times in order to cover the retreat of what remained of Hollis’ and Brooke’s regiments toward Hammersmith.  By now it was late afternoon and, with the light fading and royalist forces exhausted from around four hours of combat, the opposing forces disengaged.

Once  captured, Brentford  was sacked, according to the Venetian ambassador on Prince Rupert’s orders. After drinking heavily the royalist soldiers were said to have taken “money, linnen, wollen, bedding, wearing apparell, horses, cows, swine, hens. And all manner of victuals. Also pewter, brasse, Iron pots and kettles“.  The damage was so great that parliament ordered that all parishes in London should contribute to the relief of Brentford’s inhabitants and money was still being paid for this purpose in 1654.  Whilst subsequent parliamentary news books made much propaganda from the royalist sack of Brentford, a parliamentarian search for provisions in Brentford prior to the attack must have been responsible for at least some of the spoil.

After the battle Rupert ordered one royalist foot regiment to Syon House, to the south-west of Brentford, in order to prevent any landing from the Thames by parliamentary troops in the royal army’s rear.   Whether this was on Ruthven’s orders or at Rupert’s own initiative is unclear.

Following the confrontation between the royal army and the combined parliamentary field army and London militia at Turnham Green on 13 November, the King was forced to abandon his advance on London and, after raiding into Surrey, subsequently went into winter quarters at Oxford.