Somerset saluted and then raised his hat and waved it slowly from side to side. Further down the slope a single gun stood ready. As soon as the officer saw Somerset’s gesture he cupped a hand to his mouth and ordered his gun to fire. Flame and smoke spat from its muzzle and a loud boom echoed around the valley.

That was it then, Arthur mused silently. He was committed now. All four columns would have heard the gun and begun to carry out their orders. Already he could see the leading elements of Hill’s column climbing the western slope of the Heights of Puebla, towards the detachment of enemy soldiers on the crest. Within the half-hour the French had realised the danger to their flank and two battalions set off to climb the Heights and block Hill’s progress along the ridge.

The faint crackle of musketry carried to Arthur’s ears as he watched the brief skirmish between the Spaniards leading the attack and the French detachment. Then the tiny figures of the enemy soldiers broke away and began to retreat to the east.

‘First blood to us, my lord,’ Somerset remarked. ‘Though I think General Morillo’s men will find the next French position somewhat harder to carry.’

Arthur nodded as he looked at the enemy soldiers formed up across the ridge. Already, two more battalions from the second line had started to climb the slope to form another line to block the advance of Hill’s column. ‘That may be so, but Marshal Jourdan is doing as I hoped he would. Let him become preoccupied with his left flank and he will be undone in due course. Send word to Hill to extend his attack along the lower slopes. The more we can do to draw the enemy’s attention towards Hill’s column, the better.’

As the morning wore on the fighting along the Heights intensified as the men on both sides fought it out across the slopes, which were strewn with boulders and stunted bushes. The French steadily fed more men into the fight, weakening the centres of the first two battle lines. At eleven o’clock, Arthur saw the third line of the French army redeploying to face the north as it began to cross the river.

‘See there?’ Arthur raised his arm and pointed the movement out to Somerset. ‘The French must have spotted Graham’s fellows.’

Somerset tilted his head slightly and strained his ears for a moment. ‘I cannot hear any sounds of firing to the east, my lord.’

‘Nor I. That is to be expected. Graham’s orders were not to begin his attack until after Dalhousie emerged from the hills.’ Arthur frowned. ‘Where the devil is Dalhousie? He and Picton should have reached the river by now.’

‘Do you wish me to try to find them, my lord?’