The Wikipedia page for the battle is actually quite extensive and was the base for the orders of battle, and the period map below was used to design the field and the deployments
Above looking at the battlefield from the East to Castalla and down the allied lines. The large force of British stationed in and around the town can be seen, with cavalry pickets below it. In the distance the columns of Spanish troops marching to the west can just be seen; whilst in the foreground the French cavalry Division is close to the stream.
Seen from behind the French lines below, their three infantry divisions can be made out, looking up the hill at the redeploying allies.
The French were under the overall command of four players, with Martin as Suchet - taking General Roberts Division as well; and Laurie, Richard and Andy taking on other divisions - Habert's, Harispe's and Boussart's respectively. Most of the French were deployed in column, but one battalion on their right was deployed - as on the day - wholly as skirmishers.
The allies had three commanders. Phil took the Spanish of Whittingham and the Italians of Adam on the British left.
Gaz took the overall command of Murray plus Mackenzies troops in the centre and Roche's Spanish.
Whilst Alex took the troops of Clinton on the British right facing the cavalry division.
The game began with the French taking the first turn and Martin recognised - the fairly obvious but historically accurate fact - that the Spanish marching with their flank exposed were vulnerable to a general attack. He immediately ordered a full advance, to charge where provident the enemy. Unlike virtually every other engagement Martin has ever played in Black Powder, his troops immediately and actively responded to his command and Phil found his Spanish ambushed by a French assault!
Most of the Spanish managed to turn and face the attack, but the 5th Grenadiers bringing up the rear failed to respond in time, living up to Wellington's prejudices about Spanish troops. The continued to disappoint and routed the field; leaving a dangerous gap in the line.
To the East the French cavalry under Andy's command initially refused to advance, so the Allies under Alex were allowed time to prepare for their potential attack. A Battalion of British deployed in advance of the main line formed square, fully expecting the 13th Cuiriassiers (in one of their few actual battles in Spain) to attack. Alex decided not to sit in the town and wait for the attack, but rather advanced his troops to shut the open door the withdrawal of Roches men to their rear had created.
To the West the Spanish were barely holding, and the rest of the French were beginning to close.
Back to the East and the Cuiriassiers, supported by a regiment of dragoons ignored the British square and charged the squadrons of light Dragoons near the bridge, The British counter charged, and received support from the Spanish Hussars to their rear. The French hoped for support from their own Hussars, but having been sent to the east of the river, they got bogged down in flooded ground. The attack was a disaster for the French, with a bloody draw leaving the 13th shaken and forced to retire. Losses were similar to the 20th Light, but given the British had fought off a thousand cavalry with only 250 men they weren't complaining!
Alex folled this up on his turn by breaking his square and advancing in line on the French cavalry, he then delivered a devastating first volley to the 13th, who panicked and scattered:
By this point however Phil's Spanish had been destroyed, with the French repeatedly concentrating force on the end of the line and delivering crushing flank attacks on battalion after battalion. Fortunately Roche's brigade had arrived to hold the line, and som squadrons of spanish cavalry helped to keep the French at bay. The British infantry, with support of their Italian regiments tried to hold the centre, and used artillery to slow the advance of Laurie's division.
The problem was that the allied flank was effectively turned, and the French could now consider the fight to be on an equal footing at worst, and indeed found themselves with an effective reserve. The Spanish of Roche were untried and unreliable, but fought with admirable bravery to prevent a French breakthrough.
Back in the East, Andy's luckless cavalry saw an opportunity to use the one good bridge and raise road to attack advancing infantry in the flank. But their move proved too slow, and instead the allies were able to deliver two devastating volleys as the Hussars crossed the bridge. Suffering horrible losses they broke and fled. Thus a line of retreat for the allies was secured.
Which was just as well, for by now Martin's French had bludgeoned their way through Gaz's reserve, and Phil's Italians had suffered a similar fate at the hand of Richard's brigade. Only Laurie was being held at arms length by advancing redcoats hoping to counter his advance and stop the merciless fire of the grand battery. By this stage however 3 out of 5 of the allied brigades were broken, and the game was declared a French victory.
The whole game took about three hours to play using Black Powder, despite the huge number of models and my umpiring! History was overturned from a similar starting point, with the French victory coming from a similar gamble but running contrary to events of the day. Two hundred years ago the French attack was held by the Spanish, and the attack on the British regiments faltered. The French cavalry division was sent so far to the east, aiming to outflank and hold the defenders of the town, that it played no part in the actual fighting.
Another excellent afternoon of entertainment.