And that was when the grumbling started, as Titus had predicted to Mardina. She knew that many of the legionaries had never gone further into the jungle than you needed to take a discreet piss. Now they weren’t happy at walking into the great green chamber of the forest, past the slim columns of the tree trunks, under the dense canopy that excluded so much of the light, with the antis like elusive shadows all around – and the legionaries jumped at every crack of a twig, every hiss of a snake or clatter of scorpions.

But the complaints lessened after an hour or so, when they reached a clear path – not a metalled road, it was mere dirt beaten flat by bare feet, but it was a straight path heading directly west, and all but concealed from the sky by the trees. After the confusion of the denser jungle the column quickly formed up in good order once more, and the march to the west continued.

Another hour and they passed through an anti village, round huts built on frames of branches and walled with reeds, the people all but naked, some at work skinning animals or pounding grain or tanning leather or tending fires. The antis stared curiously at the legionaries – and they stared back with interest at the bare breasts of the women, and with horror at the elaborately pierced penises displayed by some of the men. Everybody seemed to be tattooed, Mardina thought; faces like the jaguars of local mythology peered at her from every shadow. She was poignantly reminded of the tattoo on her own mother’s face.

Soon the village was behind them, and the march continued along another straight track. Some of the walkers peeled off to fill flasks from the stream that watered the village.

This was to be the strategy, to keep to the deep forest tracks as much as possible – to exploit what the antis had built here. For this was the real anti culture. Mardina herself had seen a little of it, and from their arrival here Quintus Fabius had sent out his scouts to study every aspect of their environment. The antis were not town dwellers like Romans or Incas, but they were not savages living at random in the jungle either. The Roman scouts had found a network of settlements and trails cut or burned into the forest, neat round clearings connected by dead-straight lines, all invisible from outside the forest, and mostly screened from the air by the forest canopy. And it was these tracks the Romans would follow, as far as possible, relying on the support of friendly antis as they travelled.

It might work, Mardina thought. The Inca state seemed to have an ambiguous relationship with the antis. In theory they were mitimacs, taxpayers like every other citizen of the empire. And they did make tributes when the assessors came calling, from the produce of the forest. Their wiry archers would also serve in the Inca’s army, and reasonably disciplined they could be too. On the other hand, the Sapa Inca would occasionally order his troops to make forays into the forest, seizing goods with the excuse of unpaid mit’a, or even taking antis as slaves, yanakunas – but there could be anti raids on unwary ayllus too. It was a wary relationship then, between two quite alien cultures. But on the whole the Incas seemed content to allow the antis to live their lives under the cover of their forest canopy, invisible even to the vacuum-eating Condors. And the antis were useful to the Romans now.

So here they were: Roman legionaries marching through a three-thousand-mile-long habitat in space, and Mardina was one of them. When she thought about it, she was thrilled.

They had walked about seven hours when the surveyors said they had covered twenty miles, the standard target for a marching day.

They came to a clearing, perhaps once occupied by the antis but now abandoned, with the scuffed and blackened remains of old hearths pierced by the brilliant green of saplings. The men broke formation, dumped their packs, and changed their boots for camp sandals to ease their feet. They looked exhausted to Mardina; they weren’t in as good shape as Quintus might have hoped. But they would toughen up – and their work for this day wasn’t yet done.

With the spades they carried on their packs – tools they had been allowed to keep on arrival in the habitat – the legionaries got to work creating a camp for the night. Some worked around a perimeter sketched by the surveyors, digging a ditch and building walls. Others hastily assembled spiky caltrops from fallen tree branches and scattered them around the perimeter. Soon the tents went up, sheets of heavy leather carried by the yanakunas, in neat rows along what was effectively a narrow street, with latrine ditches threading out of the camp. Meanwhile the fires were lit, the pots were set up, and the smell of cooking filled the air, mostly a broth of guinea-pig meat and vegetables and fish sauce.

Outside all this, the wives and other camp followers made their own arrangements for the night, as best they could. The glow from the Inti windows faded, and the eerie night of the habitat drew in.

Quintus Fabius sought out Mardina, where she was helping Titus Valerius and his daughter with their meal. The centurion beckoned to draw her away.

Together they walked around the perimeter of the camp. The centurion growled, ‘Oh! What a relief to talk decent camp Latin again, without trying to curl one’s lips around runasimi, or to have Collius whispering in one’s ear … So what do you think of your first day on the march, my newest legionary?’

That title, casually used, thrilled her. ‘Impressive,’ she said truthfully. ‘The discipline, despite all the grumbling.’

‘Soldiers always grumble.’

‘And the way they put together this camp—’

‘Centuries of tradition and years of training. But the men like their camps. It’s the same every night, as if you aren’t travelling at all – as if you’re returning home each evening to the same miniature town. Soldiers like familiarity, above all. A place they know they’ll be able to sleep in safety.’ He glanced at the engineered sky. ‘We made good progress today.’

‘Yes. I spoke to the surveyors. It’s one advantage of having a sky that’s almost a mirror image of the ground. They say it’s fifteen or twenty days’ march to the ocean, if we do as well as we did today.’

‘Well, that was pretty much the plan.’

They came to a stretch of the wall that was less satisfactory than the rest; he scuffed some loose earth with his sandalled foot, and glanced around; Mardina could see he was making a mental note regarding some later discipline. They walked on.

‘To tell you the truth I’m glad to have them on the march at last. Legionaries need to be legionaries; they’re not cut out to be farmers and taxpayers – not until they retire, anyhow. We have had some discipline problems – more than you were probably aware of. Bored men squabbling over gambling games, or women, or boys. As for the positive side, I ran out of excuses to issue phalera and other wooden medals for basic camp duties. Well, Mardina Eden Jones Guthfrithson, I’m glad you saw little of that, and I’m glad you see us at our best – doing what we do best, short of giving battle, that is.’

She plucked up the courage to speak frankly. ‘And you’re speaking to me like this, sir, because—’

He stopped and rested a hand on her shoulder. ‘Well, you know why. You have a duty of your own to fulfil, you and Clodia. Tomorrow you’ll be led out of the forest by a couple of antis, and you’ll meet the tocrico apu Ruminavi and other agents of the quipucamayoc, who will take you to a capac nan station and deliver you into the hands of the Sapa Inca’s tax collectors …’

‘Tomorrow? I didn’t know it was as soon as that.’

‘I thought it best not to tell you. To let you enjoy as much of this as possible.’ He squeezed her shoulder harder. ‘You know the plan. Of all of us, yours is perhaps the most difficult duty to fulfil. Even more than poor Clodia Valeria, who I suspect understands little of this.’