‘Easy there, lad,’ said Macro. ‘The noise outside will cover any that we make. And we can shift the bolts nice and slow.’

They took firm hold of the iron bolt and began to heave again. With a gentle rasp the bolt moved and a moment later slipped free of the receiving bracket. Fearing that the hinges might be as noisy as the door, Cato pulled it open carefully, just wide enough to admit himself and Macro. The light spilled across an empty stone floor and cast long shadows before the two men as they slowly entered, squinting into the shadows as their eyes adjusted to the gloom. It was a large space, eighty feet deep by half as much in width. Overhead the beams were high above the floor and a latticework of timbers supported a tiled roof. There were two narrow slits in the wall, high up, to provide light and ventilation, but not wide enough for even a child to squeeze through.

Cato bent down and scraped up some of the dust and grains from the floor. ‘Looks like there has been wheat here.’

Macro nodded as he glanced around. ‘If every chamber in this place is as big as this one, then there’d have been enough here to feed Rome for months. Let’s try the next one.’

They worked their way round the warehouse yard, but every chamber was empty like the first. The only contents were a few coils of rope, blocks and tackle for unloading heavy items from the beds of wagons and a pile of torn and grimy sacking in the corner of the yard. In every chamber there was the same evidence that wheat had been stored there, and from the condition of the grain scattered on the floor, recently at that. When they closed the last of the doors Cato stepped back into the middle of the yard and folded his arms, frowning.

‘Where has it gone?’

‘Cestius must have thought this place was not safe,’ Macro reflected. ‘He must have figured that Narcissus and his agents would eventually discover where the grain was stockpiled. It’s been moved on.’

‘Without anyone noticing? You don’t shift that much grain without drawing attention to it.’

‘Unless you did a small amount at a time. Not enough for people to take notice.’

Cato thought briefly. It did not seem possible for Cestius to relocate his entire stock in limited movements in the time available. Even then there was another question that would need answering. ‘Where would he put it all?’

‘Another warehouse, perhaps?’

‘Someone would have seen something.’

‘In barges then, taken downriver to Ostia and stored there as soon as they bought each grain consignment.’