Though the parliamentarian infantry arrived too late to engage, the sight of the foot approaching the field caused the royalists to mount their charge sooner and with less order than they would otherwise have done. First the forlorn hopes of dragoons on both sides started the action in a ‘sharp encounter’. This is likely to have involved the dragoons dismounting and moving forward of the main bodies to exchange musket fire. This would accord with normal dragoon practice of fighting on foot and significantly, later in the action, the royalist dragoons, who were by then behind their cavalry, were left standing when their cavalry fled.

After the initial action by the dragoons, the main bodies met in the ‘plain’ that separated the two hills. Cromwell led the vanguard in the first charge and as he did so, when he got within half a pistol shot distance of the enemy, his horse was killed beneath him. As he recovered he was knocked down again by a royalist, probably Sir Ingram Hopton. Though the royalist commander later reported that Cromwell had been killed in the encounter he did in fact manage to recover. He remounted a led horse, a number of which were kept in reserve for troopers and officers to remount in such circumstances, and rejoined the action.

The royalists claimed their left division broke the opposing parliamentarian horse, Manchester’s regiment, but their right two divisions under Savage were broken by Cromwell’s regiment’s first charge. The parliamentarians broke in amongst them causing them to flee and, as they did so, they disordered their reserves, causing the whole army to rout. Although Manchester’s claimed it was the second charge that broke the royalists, all the other accounts make clear that it was this first charge by Cromwell that broke the royalists and they would not stand another charge.

Fairfax, commanding the reserve was himself involved in a flank attack on the royalists. It is possible that this was a response to the success on this side of the field of Ething’s and Henderson’s division, breaking Manchester’s regiment. However three of the accounts suggest that Fairfax did not engage until the royalists were already broken. The infantry regiments under Hobart did not arrive until this point and so they did not engage at all, the enemy having fled. In this flight the royalist dragoons, who were on foot behind the royalist cavalry having fulfilled their duties in the opening action, were left behind and captured or killed. What is clear is that Fairfax had the chase and execution of the royalists as they broke and fled. Pursuing them for four or five miles, they killed many and took even more prisoners, leaving a trail of broken equipment and dead men and horses all the way to Horncastle. Some are even said to have drowned in the river at Horncastle as they attempted to escape.