An unusual engagement in two halves. Lord Henry Wilmot and a relief force of 1,800 cavalry first engaged and drove off only the horse of Waller's Parliamentarians, then marshalled and returned to the field where they proceeded to do the same to the foot. A crushing defeat for Sir William Waller.

Following several days of siege in Devizes, the Royalists under Hopton were running short of ammunition (after the disaster with the ammunition wagon after Landsdown Hill). A relief column of 1,800 horse under Wilmot arrived from Marlborough and engaged the Parliamentarians under Waller on the downs outside the city.

The most unusual thing about this encounter was that the relief only comprised horse. They split into two brigades, and directly assaulted the 2,000 parliamentarian cavalry on the flanks of the formation, routing them, and driving many over a steep hill, the bottom of which is still known as 'bloody ditch' . The foot regiments in the centre were not engaged, and lacking direction (their officers were driven off with the horse) and fearing to fire into the mass of engaged horse the stood inactive.

Once the Parliamentarian horse had been driven off, the 2,500 foot were left in an empty battlefield, although by the time the Royalst horse had ralied and returned to the field, the Cornish foot were issuing from the city to join the fray. Wilmot marshalled his cavalry in good order and with the Cornish preventing escape they charged the Parliamentarian foot and cut them down.

This action effectively destroyed Waller's army and allowed the Royalists to take Bristol.