The Battle of Prestonpans began when the two armies came into sight of each other in the early afternoon of 20 September 1745. The Jacobites seized the high ground at Birslie Brae, west of Tranent, with the Government forces preferring the open coastal plain to the north (map 1). Both armies sent scouts into the ground between them, exchanging a few shots and jeers, but the marshes and ditches of the Tranent Meadows prevented either force from attacking.
As night fell, the armies settled down to an uneasy rest, the Jacobites having moved to the east of Tranent (map 2). The British soldiers set pickets and patrols, and lit bonfires near the only dry paths across the marsh to prevent their being surprised. The Jacobites left Lord Nairne's brigade at Birslie Brae to keep the enemy's attention fixed to the south. They made a brief feint towards Bankton in the darkness.
Late into the night Robert Anderson, who lived in the area and whose father had been out in the 1715 rising, described to a fellow Jacobite officer a pathway past Riggonhead Farm which would bring the army onto the plain near Seton. This was then reported to the Prince, who had the route recoinnoitered and decided to risk a pre-dawn flanking march. This famous march could have ended in disaster if they had been counter-attacked whilst crossing the marsh, or even if General Cope detected it and slipped away to reoccupy Edinburgh. But it was the quickest route to forcing the battle the Jacobites yearned for.
The British army fired its signal cannon around 5am on discovering the Jacobite approach from the east. The men were roused and drew up for battle, wheeling their line to face the new threat (map 3). Their line of deployment is illustrated on the left, with the cannons clustered on the right preventing Gardiner's Dragoons from positioning properly. The Jacobites drew up with their front line in two wings, with the Prince leading a second line behind. They attacked as soon as they were all formed, unwilling to wait on an open plain against an enemy with greater firepower.
The Jacobite attack was swift and ferocious. The line formed into dense blocks of Highlanders who gained pace as they crossed the stubble field. The cannons fired at them but then the crews fled, sewing disorder in Gardiner's Dragoons. The cavalry on both flanks of the British line began to back away rather than getting caught in static line, but this quickly degenerated into a rout as Jacobite musketry unsettled the poorly trained horses. The columns of clansmen charged through the redcoat musket volleys and smashed into their line, sending it reeling backwards, fracturing and splintering as it did until the whole army was in headlong flight. The Jacobites pursued, slaying up to 450 men to their own losses of around 50. Trapped on the field by the walled estates around Preston, more than a thousand fugitives were capture. After the hours of manouevring the previous day, the confrontation when it came had been shocking in its speed and decisiveness.
Re-enactors from across the UK gather to present the Battle of Prestonpans at the 2018 living history weekend.