Whilst I am prepared to consider alternate interpretations, this is another stitched shot of what appears most likely to have been the position of the Royalist left flank and that part of the field where most of the fighting took place. Note: the wrap effect has contracted the line marking the town edge and should rest about 90 degrees to the left.
This is the position accepted by Harrison and Brown's Getmapping publication 'British Battles' (Harper Collins 2002) as being the advance of the King's and Richard of Cornwall's wards (leftand centre respectively). Whilst the town's edge had most likely not advanced this far up the Downs by 1264, it nevertheless remains the direction from which the King's army emerged to advance up the slope toward de Montfort - positioned in front of the scrub line (top right).
As far as I am aware, no excavation of any sort has been undertaken of the Lewes battle site. I have not as yet undertaken any enquirey into extant town or country records to discern what ground works may have been undertaken since. Having said so, I will be making observations based on the assumption that the ground more or less remains undisturbed - the fields currently utilised as protected grazing pasture both sides of the lane, much the same as they are recorded as having been utilised just prior to the battle. The lane runs along what is understood to be an ancient way - a natural rise or fold, to the right of which lays the higher ground and the left (in shot) being a lower lying field.
The ground falls away to the left and walking this battlefield helps to explain much of what transpired during the battle and more importantly, why. Richard of Cornwall's ward took centre stage (immediate foreground) and the King's was the left most (to the left, rear of the shot) and on a slightly rising approach. Much is talked about the timing of the Royalist attack and criticism levelled (perhaps rightly) at Prince Edward and the main body of cavalry which comprised the entire right most ward.
What seems certain is that Edward and the right ward advanced ahead of the rest of the army up the slope toward the baronial left flank: the men of London, positioned at the top of the higher, chalky ground to the right of the track and the shot above. How soon the King was able to mobilise after this charge had commenced is not so certain. In any event, the Royalist army was committed to an attack and both remaining wards (containing some elements of cavalry and all of the infantry) began the advance.
What becomes clear as you walk the field is that the ground, as it falls away from the track-way, naturally leads those traversing it to the left and down into the lower ground of the pasture. Indeed, an aerial view of the ground shows the field to the left of the track-way narrowing at the top of the downs, in effect funnelling any sizeable body of men into a narrower front as they make their slow progress toward the top. The second understanding gathered from re-tracing Richard's ward is that as you roll across to the left, all sight of the field to the right of the track-way is lost. In other words, as Richard's ward would invariably have drifted away from the dividing track-way and into the approach of the left-most ward, any contact with or observation of Edward's cavalry would have proved impossible.
Before long, King Henry and Richard of Cornwall's men would have merged and unit cohesion may have been lost in a muddle. At best, the essenntial momentum for infantry ascending up the Downs would have been lost as captains struggled to keep unity and order. One can only imagine the psychological difficulties faced by the commanders of motivating their infantry to continue up the long slope without the assurance of seeing their heavy cavalry and in the face of a formed and steady enemy, occupying the high ground.
The ground to the right of the track-way is quite different from that to the left. The ground is higher that the left approach from start to finnish and rises evenly. The top soil is also very thin, beneath which is chalk. In fact, the difference in soil content and drainage is readily apparent from the aerial photography in the abovementioned 'British Battles'. Should it have rained for forty days and nights, no improvised earth works would have been possible (pits to impede horses) nor would stakes have been readily deployed which would normally have afforded the London foot of the baronial left flank some protection from the charge of the Royalist horse. The firm, even hard ground provides perfect conditions for the deployment and movement of cavalry, especially important for heavy cavalry of this period.
From the royalist right flank approach, the high ground does fail in one respect - it affords no observation of the left of the Downs. Should the horse even have been looking to the King's and left most ward, they most likely could not have made any sighting until the infantry had advanced significantly toward the top of the Downs. How far forward the royalist foot reached is unknown but de Montfort did advance his force from the heights to meet the King's army and I would suggest his timing would have achieved best advantage should he have aimed to engage them half way down the top of the Downs. Is seems unlikely that the Royalist foot would have made it into view by the time their cavalry had achieved the breakthrough at the top of the Royalist right flank. In any event, we are told that the Londoners collapsed in the face of an overwhelming heavy cavalry charge and that both sides were swept away in an uncontrollable rout and pursuit. In other words, should the Royalist foot have achieved mutual sighting of their own right flank near the top of the Downs, is seems unlikely that any of the horse remained on the field to be seen.