Battle of Roundway Down The Battle of Roundway Down was fought on 13 July 1643 , during the First English Civil War . A Royalist cavalry force under Lord Wilmot won a crushing victory over the Parliamentarians under Sir William Waller who were besieging Devizes in central Wiltshire , which was defended by Lord Hopton . Roundway Down and Oliver ' s Castle are about north of Devizes and now form part of the North Wessex Area of Outstanding Natural Beauty . Campaign . On 5 July , Hopton ' s army had driven Waller from his position at the indecisive Battle of Lansdowne . In doing so they suffered many casualties and desertions . Sir Bevil Grenville , the popular commander of Hopton ' s Cornish troops , was killed in the battle . Hopton himself was temporarily blinded the next day by an exploding ammunition cart . The explosion also left the army very short of gunpowder . The Royalist army was forced to withdraw towards Oxford , the Royalist capital , so that they could receive reinforcements and supplies . Although Waller ' s army had been forced to withdraw , it remained intact , and Waller soon obtained reinforcements from the Parliamentarian garrison of Bristol . He followed up Hopton ' s army closely , and on the night of 8 July he occupied Roundway Down , the high ground north of Devizes , barring the Royalists ' further retreat . The Royalists fell back into the town , and their commanders held a hasty council of war . It was agreed that Prince Maurice would break out and make for Oxford with the 300 cavalry remaining with the Royalist army . While Hopton ' s Cornish infantry defended Devizes , Maurice was to collect a relieving force from Oxford . Prince Maurice and his 300 horse escaped just before Waller surrounded Devizes . Unaware of Prince Maurice ' s escape to Oxford , Waller set up his guns and began a siege of the vulnerable unfortified town the next day . On 12 July he captured a convoy bringing ammunition to Hopton , and demanded a surrender . This was refused , and the next morning , the Royalist relief force appeared on Roundway Down . Prince Maurice had reached Oxford late on 10 July . Lord Wilmot , Lieutenant General of Horse for King Charles , set out almost at once for Devizes with 1 , 500 cavalry and two light " galloper gun s " , an early form of horse artillery , collecting Prince Maurice ' s 300 horse on the way . The battle . Early on the morning of 13 July , Wilmot ' s relieving force reached Roughridge Hill , north east of Devizes , and fired two rounds from their guns as a signal to the besieged . They were organised as two strong brigades under Wilmot himself and Sir John Byron , and a weaker one under Lord Crawford . Waller had been informed of their arrival , and he abandoned the siege and marched to Roundway Down , hoping to defeat Wilmot before Hopton could sally from Devizes against his rear . He deployed his infantry and artillery in the centre of his line , with cavalry on each flank . Recent findings of cannonballs and musket and pistol shot have suggested that the site of the battle was not in fact on the highest point of the down , but close to Oliver ' s castle in front of what is today the Roundway Covert . Although Waller held the higher ground , the Royalists attacked first . Wilmot ' s brigade attacked the Parliamentarian left . The leading troops of this Parliamentarian wing were a fully armoured regiment of cuirassiers , the London lobsters under Sir Arthur Haselrig . They appeared to have met Wilmot ' s charge at the halt , and were thrown into confusion and driven back into their second line . After a brief contest , they retreated in disorder . Byron attacked the Parliamentarian right , commanded by Waller , under fire from the guns and musketeers of their centre . Once again , the Parliamentarians halted to receive the charge , and were shaken by the clash . They too gave way and fled , pursued by Byron . Some of the fleeing Parliamentarians died when they were forced to gallop over an unseen precipice which is now called Oliver ' s Castle and is near Roundway village . Wilmot ' s and Byron ' s troopers rallied and turned on the Parliamentarian centre . They captured at least four of the Parliamentarians ' cannon and turned them on the infantry . The 2000 Roundhead foot held out for a while , until Hopton ' s infantry who had marched up from Devizes castle deployed to attack . The Roundheads then tried to retreat northwards , but failed and the survivors threw down their arms . About 600 Parliamentarian troops were killed and about 1 , 000 were captured . Aftermath . Roundway Down was the greatest cavalry victory of the English Civil War . The Royalists christened the battle " Runaway Down " . The defeat of an army arrayed in proper battle order on high ground by a column of cavalry that had just ridden down from Oxford was regarded as remarkable . Waller had previously been favoured to replace the Earl of Essex as Lord General of the Parliamentarian armies . His defeat at Roundway Down made this impossible . Waller and his supporters criticised Essex for his perceived inactivity , which had allowed the royalists to detach Wilmot ' s cavalry from Oxford . The Parliamentarian field army in south - west England was destroyed , allowing the Royalists to capture the port and major city of Bristol a few weeks later ; this period of Royalist successes was referred to as the " Royalist summer " . The " village " of Roundway is today a small hamlet north of central Devizes , with a population of around 25 residents . There is a discussion of possible burial sites for the battle on the Devizes heritage website with an outline of the research evidence .