To Napoleon’s left there was a rumble of hooves and he turned to see the cavalry reserves moving forward to form up behind the line of guns being trained on the ridge. Regiment after regiment of cuirassiers, lancers and dragoons came forward until the floor of the shallow valley was a mass of horsemen, sitting silently in their saddles as they awaited the order to attack. Ney took his place at their head and raised his feathered hat to signal the guns to open fire. With a staggered roar the bombardment began. Each gun spat flame and smoke as it jumped back a short distance with the recoil.

Wellington’s gun crews stood to, but did not return fire, and Napoleon realised that they must be conserving their ammunition for the French cavalry, when they began their advance. Napoleon saw one of the British gun carriages above Hougoumont disintegrate as it was struck by roundshot. Splinters exploded in all directions, felling the crew. The axle collapsed and the barrel canted up at an angle towards the sky. All along the ridge columns of earth tore into the air, but the lines of soldiers still stationed on the forward slope and the ridge itself stood their ground as roundshot, canister and shell decimated their ranks.

‘They cannot take such punishment for long,’ Soult commented.

Napoleon nodded. But even as he took grim satisfaction from the destruction being dealt out by the French guns, he was aware that time was slipping away. Every minute brought the Prussians closer to his right flank. The battle could still be won, he calculated, but the odds were no more than sixty to forty in his favour. Victory depended on breaking the centre of the allied line. Napoleon reached down and took out his fob watch, and glanced at the hands. Wellington’s soldiers, scraped together from the forces of Europe’s minor powers, had defied Napoleon for over four hours.

‘Their nerve will break at any moment, Soult. I am certain of it.’ Napoleon gestured towards the waiting cavalry. ‘And then nothing will stand between Ney and the streets of Brussels.’

The elm tree, 4.00 p.m.

Even though Arthur had given the order for the battalions on the ridge to lie down the casualties were still fearful. Heavy shot, angled low, smashed through the prone figures, leaving bloody smears and tangled bodies to mark their passage, and there was no shelter from the shells that regularly exploded overhead, sending fragments of iron slashing through the men below.