'Let me guess,' smiled the bet-taker as he sized Macro up and calculated his worth. 'You'll have a gold piece on Porcius, to win.'

'Er, no.' Macro felt embarrassment burning in his cheeks. He glanced round and continued in a low voice, 'Five denarians on Nepos, to win.'

'Five denarians?' The bet-taker looked disappointed. He quickly reappraised the centurion, and continued sarcastically, 'Sure you can afford it?'

Macro stiffened. 'Yes, of course I can. Five on Nepos, like I said.'

'Nepos? You know the odds are ten to one?'

'That's what I'm counting on.'

'Well, it's your money. If you're sure…?'

Macro frowned. 'Do you want to take the bet, or not?'

'I'm happy to take your money. Just a moment, please… sir.' The bet-taker opened his tablets and prepared to make a new entry with his stylus. He began to press some tiny notation into the wax, muttering as he wrote. 'Five den. on Nepos to win… Your name?'

'Centurion Macro.'

'Macro. Fine, now if I can just have your payment.' Macro handed him the silver coins from his purse and the bet-taker dropped them into one of the boxes carried by his heavies. The coins fell through the slot with a dull chink on to the money already taken in. The bet-taker nodded to the man carrying the chest. 'That's tally one hundred and forty-three.'

The ex-gladiator raised a large metal hoop from his side and fumbled amongst the small wooden pegs until he reached the right number and then worked it free and handed it over to Macro. The bet-taker smiled at him. 'Pleasure doing business with you, though I doubt we'll meet again. Now, if you'll excuse me…'

Macro tucked the wooden tally into his purse and hurried back to Cato.

'How much did you place on Nepos?'

'Enough,' Macro replied easily, then pointed across the heads of the spectators towards the imperial box. 'Look, there's Claudius' flunkies. He must be on his way.'

'How much?' Cato persisted.

'Oh, five denarians, or something.'

'Five den-Macro, that's pretty much all we have.'

'Actually, it is all we have.' Macro shrugged an apology. 'It's a risk, but I got odds of ten to one.'

'Really?' Cato responded sourly. 'And why do you think that's good news? He's got nine chances in ten of losing.'

'Look here,' Macro lowered his voice, 'our man said it was a sure thing. We stand to win fifty silver pieces when it's over.'

'I can do the maths, thank you. Fifty pieces, if Nepos wins.'

'He will, trust me. I have a feeling for these things.'

Cato shook his head and glanced away, letting his gaze turn to the imperial box. The household slaves were busy setting up a table of snacks and wines to the side of the Emperor's seat. Even at a distance of fifty paces, Cato could make out a platter of ornately arranged fowl glazed in what looked like honey. His mouth began to water at the sight and he felt his stomach churn with hunger.

The imperial household began to emerge from their private entrance to take their seats. A handful of favoured senators eased themselves down on to plump cushions set on the stools each side of the imperial dais. They were followed by some of the Emperor's freedmen and scribes, who stood at the back of the box. At last the white tufts of hair and the gilded wreath on top of Claudius' head came into view and a great roar of greeting swelled up from the crowd and echoed around the Great Circus. Louder than a battle, Cato thought. Far louder.

The Emperor stood still for a moment, basking in the popular acclaim. Only his head moved, in the characteristic twitch that no amount of self-control could prevent. At length Claudius slowly raised an arm and turned to greet his people, who responded to the gesture with an even greater roar. The Emperor's arm sank back to his side and he climbed on to the dais and slumped clumsily into his seat. As the Emperor's wife, Messalina, stepped up beside him, the cheering reached a new frenzy.

Macro leaned close to Cato and shouted into his ear, 'From what I've heard, I bet there's quite a few amongst them who know her almost as well as her husband.'

He grinned and Cato looked round anxiously to make sure that no one had overheard the comment. That was the kind of public comment that informers picked up and passed on to palace agents for a small reward. Then, one night, a squad of Praetorians would kick your door in and bundle you off, never to be seen or heard from again. Fortunately, Macro's foolish words were lost in the deafening roar of the crowd and Cato began to relax.

Then he saw another man entering the imperial box: thin, with dark hair and a plain white toga. Claudius beckoned to the newcomer with a smile, and indicated a seat just below the dais. Cato felt Macro cup a hand to his ear as he pointed towards the box with the other.

'Did you see who just arrived?'

Cato nodded. 'Our friend, the Imperial Secretary.'

'Do you think Narcissus knows we're back in Rome?'

'If he doesn't already know, he will soon.'

'Then we're in trouble. That bastard talked General Plautius into decimating our cohort.'

'I remember. He won't be happy that I'm still alive.'

Cato felt a surge of fear as he looked over the heads of the crowd at Narcissus. Not much escaped the notice of the man who controlled the Emperor's secret police, disposed of any threats and dispensed much of Claudius' patronage. And if he did know that Cato was in the city then he would be sure to tie up any loose ends as soon as possible, preferably by discreet strangulation in some dark, forgotten cell of the Mammertine prison. But there was a chance, an outside chance, that Macro and he had evaded the ever watchful eye of Narcissus, even now.

At that precise moment Narcissus turned in his seat and cast his gaze over the crowd and, before Cato could react, his eyes fixed in the direction of the two centurions. Cato felt his guts turn to ice. It was only an instant, then Cato slumped down on his bench, out of Narcissus' line of sight.

'Shit!' Cato muttered. 'Shit… shit… shit.'

Macro dropped down beside him, alarmed by the sudden change in his friend's expression. 'What's the matter?'

'He saw us. Narcissus saw me.'

'Bollocks. How could he? We're just a pair of faces amongst thousands. There's no way-'

'I'm telling you, he saw me!' Cato could almost feel the rough hands of the Praetorian Guardsmen Narcissus would be sure to send out to arrest him. It would all be over in a moment.

Macro stood up slowly and glanced towards the imperial box, before ducking back down beside his friend. 'He's not even looking this way. Just chatting with the Emperor. Nothing else. He can't have seen you. Relax!'

The cheering quickly died away as the priests prepared for the sacrifice to open the day's racing. Two assistants dragged one of the white kid goats out from the cage and, holding the struggling animal by its legs, they carried it up the steps to the altar and held it down on the gleaming marble surface. The chanting of the high priest could just be heard across the track, as he intoned the blessing of Jupiter, best and greatest, on the Emperor Claudius, his family, the senate and people of Rome, and the charioteers. Then, he raised a curved dagger above the bleating goat, paused a moment, the blade glinting in the sunlight, before he slashed it down. The distant bleating was abruptly cut off. For a moment the priest bent over the twitching body of the goat and worked at its stomach with the dagger. Then, he eased out the liver, glistening in purple and red as it steamed slightly in the cool air. He bent over the organ to examine it closely, then called over a colleague, who also looked at the liver before they discussed their readings. The priest suddenly lifted the organ aloft to signify that Jupiter had accepted the sacrifice and the races could proceed. A huge roar of relieved tension swept round the stadium. Macro slapped his hands down on his knees and grinned like a boy.