Not having slept, my mind was slow. I asked him why.

*The people did not care for Constans, and they do not care for his Eastern brother either; there has been too much rotten fruit from that tree. But Magnentius is from the West; his home is here; people believe he will fight off the barbarians, instead of carrying the legions away to distant wars that mean nothing to them.'

He saw my eyes move to the closed door.

*You need not fear; Constans had no friends in this house. Besides, he is dead. The question is: who is emperor now? Constantius, because he is his brother? Or Magnentius, by force of arms? We all know Gratian owes his loyalty to the House of Constantine: for him the choice is clear. But he will be hard pressed to carry the province with him.'

I looked at him. It seemed a whole new world of doubt was opening up beneath my feet. *But sira"' I began; but before I could continue there was a tap on the door. It was Clemens, come to say that a deputation of city councillors had arrived.

*Tell them to wait,' said Aquinus. And, to me, *They have heard; and now they have come to ask me what they should do.'

*And what will you tell them, sir?'

His eyes met mine, and I saw the glint of humour there. *I shall tell them,' he said, *that they must decide for themselves. That will stir them up. But if you ask my own view, then I choose the path of stability; for without that we shall have the barbarians once again at our gates, and no one to protect us.' He paused, then added, *But which path is that? Which charioteer do we back? That, at the moment, I cannot tell you. Be prepared, young man. You are going to have to make hard choices. We all are . . . But come, let us see what these councillors have to say.'

He stood, and we made our way towards the inner courtyard, where they would be waiting. As we walked I asked after Marcellus.

*He has gone to the villa. He said there was estate business he wanted to attend to a" though I cannot think what was so urgent a" and that he had had enough of the city for a while. I think he missed you, while you were away. He has been sullen as a Pictish slave these past days, which is not like him at all.'

At dawn next day the palace courtyard rang with the hooves of horses a" of couriers bearing urgent dispatches from Gratian to the captains of the outlying forts, from Brancaster and Richborough in the east to Pevensey in the west. He ordered the stable-master to lead out his fine grey mare, and wearing his finest dress armour with its gold-embossed cuirass and helmet of white and scarlet plumes, he rode in procession from the palace, through the streets and up the hill to the city fort.

Overnight a dense autumn mist had come rolling up the river from the sea. It lay over the city like a mantle, obscuring our view and muffling our marching footfalls. Within the wide square parade-ground of the fort the troops of the garrison stood waiting, line after line, standing to attention, their ranks receding into the mist.

Already, in one night, rumour had spread like a heath-fire in a gale. The centurions had reported that the men were nervous. They did not like political upheaval. One sensed unease everywhere.

I saw Gratian look about and scowl at the weather. He knew the power of a fine entrance and saw the day could not have been worse. But it could not wait. He said something to Leontius, then mounted the dais.

He liked to think he had the common touch, having come from peasant stock and risen through the ranks. When he was before the troops he adopted an easy bluff, swaggering manner. Many men do it, and it can be carried off well or badly: either way it is an art, a deception, a rhetoric; an attempt to convey what is not; or, at best, to create the illusion of what once was. I do not know what went wrong on this day a" the weather, or his own mood, or something in the men a" but from the start his address to the troops was ill-starred and faltering. His words, which he had intended to be booming and uplifting, were engulfed in the damp haze like pebbles tossed in mud. He recounted Constans's murder, going on at length about the foul injustice of it. Even as he spoke, as if to mock him, the mist swirled and thickened round the dais, and the men, whom he had intended to fire to anger, stared at him in stolid silence.

Not far from where I was standing, I saw a trooper lean over and whisper something to his neighbour. His neighbour smiled and nodded and whispered back. It was an unacceptable lapse in military discipline; but the centurion at the end of the line, though he must have noticed, looked resolutely ahead. They talked on, and discreetly I turned my head to hear. Their conversation was not in Latin, but British, and though I could not hear all their words, I could tell enough. What did they care for Antioch and the Persians, and for remote divine Constantius in his perfumed Eastern palaces? Magnentius would see them right; he was one of their own. Their words were close to treason; but even as I thought this, I recalled what Aquinus had told me.

In front, Gratian was talking on, indistinct, irrelevant. I glanced once more at the centurion. He was dark-haired and olive-skinned: no Kelt then; he would not understand the troopers' words; and, judging from the look on his face, he did not wish to. Just as well, I thought. He knew enough of army discipline to know that it was not the time to haul the men out of line, with the mist descending and the troops unsettled.

I gave a loud cough into my fist. At this, one of the whispering men glanced up and met my eyes through the haze. I glared at him, and made a gesture at my ear to show he could be heard. He closed his mouth and jabbed his neighbour in the ribs; and after that they stayed silent.

Meanwhile, Gratian was losing his stride, hesitating, departing from what he had planned to say. He was losing the men, and he was too old a hand not to sense it. He hurried on, bringing the address to a swift end. Then the tribunes raised their batons and called for an acclamation. I waited, scarcely daring to breathe, for silence then would have been open mutiny. But eventually a weak cheer rumbled along the line, dying to nothing even before Gratian was off the dais.

Back in the mess hall there was uproar. As soon as I walked in, Leontius called me over. *Did you see Gratian's face? Whoever told him the garrison is loyal is in for a drubbing.'

The cadet beside him, a broad youth with lank brown hair who was in with the wrestling set, chimed in with, *They may as well have had "Magnentius" written on their shields, the dogs. I say Gratian should ship them all off to the Persian frontier to teach them a lesson.'

Leontius gave him a shove and said, *Shut up, Marius.' But I saw a fleeting veiled look pass between them a" a look that was new to me, but which I should soon come to know.

I sat down with them on the bench. That morning, while we were up at the fort, another messenger had arrived from Gaul. I asked what news there was.

*Only this,' said Leontius frowning; and he went on to tell me what had happened the night Constans was deposed.

Magnentius, he said, had waited till his tour of duty brought him to Autun, where that year Constans was wintering. On an appointed night, he invited the foremost men of the court to a banquet; they feasted late, and Magnentius made sure the wine flowed freely. When the party was at its height, he withdrew on some pretext, changed his clothes, and returned clad in imperial purple and wearing the diadem.

*He must have had supporters there, waiting for the moment. It was all rehearsed. As soon as he appeared they all cried out, hailing him as Augustus and emperor.' The other guests, drunk, and bewildered at this spectacle, had gone along with the prevailing mood and added their own voices. Then the guards beyond the door were called in, and were asked to take the oath of loyalty; after that the city gates were sealed, and Magnentius spent the rest of the night securing the garrison, the treasury, and the imperial palace.

*But where was Constans all this while?' I asked.

*Away; out of the city, hunting.'

*Ah, hunting.' I raised my brow and nodded; and this was enough to draw down on me a grim line of Pannonian faces, glaring from along the length of the mess table.

After that, I returned my attention to my food and said no more. It was later, from Catius the Spaniard, that I heard how Constans had met his end.

When the news of Magnentius's coup had reached Constans, he had vowed to fight and regain what was his. But his courtiers, the same men who had fed his vanity and promised him he was invincible, now wrung their hands and said that all was lost: the Gallic legions had already declared for the usurper. No one dared tell him, even then, with what speed and enthusiasm they had done so. Upon hearing this, Constans flew into one of his rages. Why had they not warned him? Surely someone among them must have caught a rumour of what was afoot. For what other purpose had he kept an army of costly spies?

The courtiers stared at one another, and repeated what they had already said; and eventually, as realization dawned, Constans's rage turned to terror. He would go to Autun, he said, and throw himself at Magnentius's feet. He would ask for mercy. *No!' retorted the courtiers, thinking of their own fate; better to make for the East and his brother Constantius, who would surely help.

And so Constans fled.

He had reached the town of Elne, at the foot of the Pyrenees, when Magnentius's horsemen overtook him. He ran to the church there, and sought sanctuary. The troops dragged him out, and on the steps they put him to death.

In London, Gratian summoned the Council to assembly. On the afternoon before it met, a deputation of Pannonians went to him, asking to attend him as his escort.

He thanked them, but declined. To take an armed guard into the Council chamber would be a clear sign of his distrust, just when his purpose was to persuade. The Pannonians protested. In the end, he agreed to take Leontius and one other a" but unarmed.

No one said what was becoming clear to us all, that the corps, of which we were so proud, was beginning to fracture and divide. One saw it in the mess hall, or in the chance gatherings in corridors and courtyards: Pannonians with Pannonians, Gauls with Gauls, Britons with Britons. Old friendships frayed; whispered conversations were suddenly broken off as one passed, and resumed after.

But it is generosity in adversity that one remembers. Soon after mess there was a tap on my door; it was Leontius, asking me to be the one to accompany him to the Council. He could have chosen a Pannonian, and there were many whispered complaints later that he had not. But he chose me, to show he was above the faction.

We woke next day to low grey sky and steady rain; but at least the fog was gone. At the porch of the basilica a crowd was waiting a" decurions, city officials, clerks and common citizens, all curious and afraid. The falling rain hissed on the wrought iron of the cressets; the torches flared and spluttered, sending smoke curling upwards under the coffered stone roof.

Leontius was tense. It would be an easy thing, among so many, for an assassin to strike Gratian down. From the corner of my eye I saw his hand move instinctively to his sword belt; then move away as he remembered we were unarmed. I scanned the crowd as it parted around us, looking for the telltale signs a" a conspiratorial nod, an arm seeking under a cloak, an edging forward, a sudden step. But there was nothing; and moments later we were through them, passing over the threshold of the council chamber with its tall bronze doors and marble lintel.

A hush fell as we entered. From the tiered seats the assembled decurions stared. Eyes moved from Gratian to Leontius and me, and then to the place where our swords would have been. I saw their faces and understood that Gratian was right to refuse an armed guard: these men were no threat; an entourage with swords would have smacked of tyranny.

In the front row, I saw Aquinus sitting among the senior magistrates and other officers of the Council; behind them, from the rising tiers, the decurions looked down like birds on a wall. Voices resumed. There was a buzz of tension. The air smelled of incense and lamp-smoke. Leontius and I took up our places, out of the way beside the doors; the presiding magistrate spoke a few words; then Gratian stepped forward, his boots sounding on the black granite floor.

First he outlined the military situation in Gaul, speaking disparagingly of Magnentius, calling him traitor and usurper, predicting that soon Constantius would bring his mighty armies from the East and crush the rebellion. His voice boomed; he spoke too fast. He seemed oddly ill at ease. As I cast my eyes over the faces staring down at him, it came to me that he was used to addressing soldiers, men who listened and obeyed.

Eventually he paused. The only sound was the splutter of the hanging lamps suspended on their long chains. He had not invited questions; but now, breaking the brief silence, someone from high up in the tiered seats called out, asking which legions in the West were loyal to Constantius.

Gratian's head jerked up, searching for the speaker. For a moment, before his face set, his irritation showed. Who were these civic nobodies to question him on military matters?

*They have all declared for the usurper,' he answered.

*So Magnentius holds Gaul, Spain and Italy?'

*For now, that is true.' He turned his head away, indicating that the exchange was over.

But the speaker continued, *There is a rumour that Illyricum has also declared.'

Gratian's mouth hardened.

*I did not tell you,' he answered slowly, *that the emperor would not have to fighta"'

*You mean Constantius?'

*I mean the emperor. There is no other.'

*But Constantius is at war with the Persians. He must be half a year away.'

*He will disengage, or make peace, or send another army.'

*How long,' someone else called from the back, *will it take him to assemble such an army?'

Gratian turned. His colour had risen. *A year,' he snapped. *Perhaps longer. But he will come. In the meantime, we shall hold out against Magnentius. He will not dare move east with his flank unsecured.'

There was a pause and muttering after this. Then a retired magistrate, an old squire in from the country, rose to his feet.

*Do you mean to fight Magnentius then?'

*Of course.' Gratian looked at him as if he were a fool.

*And yet Magnentius claims he is now the rightful emperor in the West. Does that not make us the rebels, if we move against him?'

I stole a glance at Leontius. He was standing rigid, but at his side his fingers were tapping angrily. He did not care for all this quibbling talk. It was not how things were done in the hill stations of Pannonia.

*Constantius,' answered Gratian slowly, *is the senior Augustus.'

*By whose authority except his own?' returned the squire. *If we resist, Magnentius will strike against us even before Constantius is ready. We must consider the safety of the province, of our homes and families.'

*Let him strike. We shall repel him.' Gratian turned impatiently away. But the old man had not finished.

*It is forbidden for us citizens to bear arms. We cannot defend ourselves. And, even if we were armed, we have forgotten how to fight. The imperial government taxes us, and in return promises us safety, not civil strife. And yet,' he said, turning and surveying the rows behind him, *three times my house has been razed by the Saxons, my livestock slaughtered or carried off, and my people murdered. Three times I have made good what I lost a" but I cannot afford to start again. Let the emperors fight their own war! We have no need of it.'

The old man sat down, chewing on his gums in agitation. There were murmurs of agreement, quiet at first, and timid, but rising in confidence and volume. The presiding magistrate beat his rod of office on the floor, calling for order. Gratian frowned at the rows of men in front of him.

*I understand what you say. I cannot support such a policy.'

The presiding magistrate asked if he would like the Council to move to a vote.

*No!' he cried, his anger at last breaking forth, *I have not come here for your vote. I shall consider what I have heard, and I will consult elsewhere. You shall have my decision when I have made it.'

In the days that followed, Gratian kept to his quarters. The palace twittered like a roost of starlings; everyone had heard that the meeting of the Council had been a disaster, that he had not received the support he wanted. In the barracks the air was tense, and among the Protectors the factions began in earnest.

Those who had been with Gratian longest, who had come with him from his command in Africa, sided with Constantius. So, of course, did all the Pannonians. The rest kept quiet, which was viewed by the others as support for Magnentius. Blood and tribal loyalty won out; and, though there was much talk, there was no place for reason.

While Gratian waited for his messengers to return from the cities and forts, we were confined to London. When I could, I called at Aquinus's town-house. Marcellus had not returned. I found I could think of little else.

Eventually I went to Leontius and told him I had a pressing matter I had to attend to.

*Take a horse,' he answered. *I'll make sure you're not missed. Two days, mind. No longer.'

The shadows were lengthening by the time I reached the avenue of poplars that led to the gate. I found Marcellus behind the house, working in the low gully beside the entrance to the hypocaust. His hair and tunic were thick with mortar-dust; he was peering into the dark tunnelled space below the house, while behind him a slave stood waiting, holding a bucket and trowel. The brickwork arch, which formed the entrance, had collapsed. It lay in a heap on the ground. Marcellus had advanced half inside; he had not seen me.

The slave looked up and recognizing me smiled. Just then Marcellus called to him, *See here, Cato, it's as I thought; the beam has collapsed. Come and help me lift it.'

I threw off my cloak and with a secret sign to the slave jumped down and crept in along the passage. Marcellus, up ahead, was saying, *Now careful, it's heavy; you take that side, and I'll take this.' I coughed, and he swung round.

*Drusus!' he cried.

I could not but laugh at the look of surprise on his dust-smeared face. I stepped up and gripped the end of the timber beam, and together we heaved it back onto its brick post. It took some little while, and when it was done we were both out of breath.

We stopped and looked at each other.

*Now you've got plaster all over your uniform,' he said. He reached out with his hand, about to dust it off; but then he hesitated, and walked back outside, and sent the slave off on some errand. Turning he said, *Why have you come?'

I drew my breath. My tongue felt like lead in my mouth. Eventually I said, *I called for you in London. You were not there. I had to see you.'

*Oh?' he said coolly. His eyes surveyed the bricks that lay scattered on the grass slope. He stooped down and began arranging them, moving them pointlessly from one side of the fallen structure to the other.

*Marcellus, what are you doing? They're as much in the way there as they were before!'

At this he ceased. For a moment he stared at the bricks, then raised his hand to run it through his hair. Then he stopped himself, seeing it was covered with mortar.

He said, *You shouldn't have left me like that.'

I spread my hands in a helpless gesture. I had been thinking all during my long ride from London what to say; but too much had depended on him.

*You were busy, or don't you remember? But it doesn't matter now. Scapula has been putting girls in your way for months. He wanted to see what I would do.'

*That's why you were angry.'

I thought of the girl in Dover and said, *I had no cause. It's not my business.'

*No? I thought I was your business, and you were mine.'

Our eyes met. And then, at last, the words came tumbling out.

*I am sorry, Marcellus,' I cried. *I had to face down my own weakness, or what use is my friendship, if I cannot for my own sake be good? I was jealous, and ashamed of it. I love you more than my own life, if you want to know; but no man can possess another. This one thing I had to find alone.'

He paused, frowning. Then he said, *You know what Scapula is saying?'

*No; what?'

*He is saying that we are lovers.'

I kicked angrily at a fallen brick. *To Hades with him! Let him say what he likes.'

*Are you ashamed of it?'

*No, Marcellus; never.' Then, looking at him, I said, *I should be proud, if it were true.'