As dawn painted the sky pink two days later Napoleon and his staff departed Alexandria, leaving two thousand men behind to defend the city under the command of General Kléber, who was recovering from his wounds. The army was striking out towards the Nile, nearly fifty miles away, and then Napoleon would lead the advance along the banks of the great river to Cairo. Desaix and the main body of the army had set out two nights before - after joining their comrades at Alexandria - tramping into the moonlit desert to cover as many miles as possible before the sun rose and turned the arid landscape into a furnace.

The air was still cool and Napoleon felt comfortable as his staff and the guides followed in the tracks of the four divisions that had gone ahead. A wide swath of churned sand stretched out before them and Napoleon was keen to re-join his army even as he enjoyed the muffled sounds of their progress. He laughed and turned to Berthier.

‘I think the sun must have got to Desaix’s head.Those reports he sent to us yesterday about the harsh conditions can’t have been true.Why, at the rate we’re marching, we could reach the Nile by tomorrow night.’

Berthier shrugged.‘It’s early in the day, sir.You know what the heat is like at midday. Besides, the men are in the wrong kind of uniform for this climate, and with the loads they’re carrying, well, it’s going be a struggle.’

Napoleon shook his head. ‘You worry too much. You saw what our men could achieve in Italy. My God, they marched for days at a time, and then fought a battle at the end of it. And that was against a proper army - not the barbaric rabble that the Pasha will throw against us. This campaign will be over in a matter of weeks, Berthier, mark my words. Egypt is as good as ours.’

‘If you say so, General.’

‘I do. Now cheer up and enjoy the ride. You won’t see landscape like this in Europe.’

‘No,’ Berthier muttered. ‘Thank God.’

But as the sun climbed into the sky the temperature rose with it and soon the very air that he breathed seemed to scald Napoleon’s lungs. By mid-morning the blazing intensity of the sunlight reflected off the sand began to hurt his eyes so that he had to squint as the small column trudged on. Shortly after midday they came across the first signs of the difficulties that Desaix and his men had encountered on the march across the desert. A knapsack lay abandoned beside the track. Napoleon was outraged.

‘Half a day from Alexandria! That’s as far as the owner of that has got before he weakened. Have one of our men pick that up. When we find who it belongs to I’ll have him court-martialled on the spot.’