The route veered off towards the reverse slope and a quarter of a mile ahead of them Arthur saw a company of redcoats, then the rest of the battalion, in an uneven line, spread across the undulating side of the ridge. The nearest men turned to look as their commander and his aide came galloping up. One of the soldiers raised his shako and gave a hoarse cheer, taken up by a handful of others as Arthur thundered by. There was little more than ten minutes before the French skirmishers reached the crest and realised the opportunity that was there to be grasped. If they could break through the allied line then each half could be destroyed in turn. Even though Busaco was as fine a defensive position as Arthur had seen in the Peninsula, that had always been the danger in trying to defend the ridge: too few men to hold its ten-mile length.

The colonel of the Eighty-eighth Foot, Alexander Wallace, saw the two riders approaching and trotted his mount forward to meet them.

‘Good day to you, my lord.’ He bowed his head. ‘And to you, Somerset.’

Arthur nodded briefly and pointed back along the crest. ‘There’s a French column coming up from the mist. They threaten to cut through our line. I need your men half a mile to the north there. At the double.’

‘At the double, yes, sir.’

Arthur fixed him with a steady look. ‘You must hold them at all costs. There may be an entire division of them. Do you think your fellows can do their duty?’

‘Aye, sir. They will,’ Wallace replied soberly.

‘Good, then see to it, as swiftly as you can.’

They exchanged a salute and Arthur wheeled his horse round and galloped back along the ridge towards the point threatened by the French column tramping steadily up the slope. At first they could see nothing of the enemy as they rode, and Arthur wondered if they had withdrawn, or changed direction. Then he saw the fold in the slope where the gully dropped away, concealing a wide breadth of ground within. The first pairs of skirmishers were already in view, cautiously moving up the slope, looking for the first sign of their opposite numbers, but the ridge ahead of them was empty beneath a warm morning sky as larks flitted low over the heather.

‘My lord, over there!’ Somerset called out from behind.

‘I see them.’