‘Yes, your Imperial Highness,’ the Minion replied. ‘And we bring felicitations. .’

‘Enough of that!’ Tiberius barked like a centurion on a parade ground. ‘I’m not interested in Rome or what it thinks of me. But I understand my good friend Sejanus has undergone some sort of crisis?’

The Minion stiffened. I hid my smile of satisfaction. I was correct: Macro had known why we were here. Was this a good augury? I closed my eyes and thought of Agrippina’s face. I prayed to whatever gods there were that I would survive this ordeal.

‘Well, come on!’ Tiberius urged.

The Minion spoke quickly, describing Metellus’s death. I looked away, trying to distract myself. In the garden beyond grew asparagus and cucumbers, Tiberius’s favourite vegetables. They were kept in boxes on wheels so they could be taken in and out of the sun according to the weather. Sometimes he would go for days, eating only these or radishes from Germany. I half listened to the Minion’s lies, until a shadow passed in front of the column. Tiberius told the Minion to be quiet. Forgetting myself, I looked up. The new arrival was tall and stoop-backed, with long-fingered hands which dangled like the claws of an animal, their nails curved and dirty. The new-comer’s face was sallow and pitted and, like Tiberius, he was bald at the front with a thick crust of hair on the nape of his neck. He came and stood by Tiberius like a faithful dog.

‘My good nephew, Gaius!’ Tiberius murmured.

By then I had lowered my eyes. ‘Little Boots’ certainly didn’t resemble Agrippina with his dull face, muddy-coloured complexion and eyes like those of an opiate-drinker. Slobbery-lipped and loose-jawed, Caligula looked like an imbecile.

‘Continue,’ Tiberius murmured.

The Minion did so in a few halting sentences. Tiberius tapped his silver-gilded sandal, an ominous sound like that of a drumbeat accompanying a victim to execution.

‘And you are Parmenon?’

Again the Minion stiffened. Tiberius’s tone seemed to be more friendly.

‘Yes, your Imperial Highness.’

‘And you can vouch for all this?’

‘I know the truth, Excellency.’

‘The truth?’ A short, barking laugh. ‘If you know the truth, Parmenon, you are, truly, a very fortunate man. You are both dismissed!’

We got up from the cushions, bowed and backed out of the chamber. The Minion was very restless. Red spots appeared high on his cheeks and his agitation only deepened as Macro told him to wait whilst beckoning me to follow him. I crossed the small atrium. Macro pushed me into a doorway, told me to stay there and walked off. The door opened and a hand dragged me inside. Gaius Caligula grinned at me. Believe me, they were a family of fine actors! Gaius’s face had changed, it was no longer slack and vacuous, his eyes were a strange light-blue, and his mouth and jaw more composed. He grasped me by the shoulder, and I smelt his wine-drenched breath.

‘Well? Does she love me?’

‘Agrippina. .?’

‘Not her! Drusilla!’ Gaius snapped, referring to the younger sister.

‘Of course, your Excellency!’

Gaius wetted his lips. ‘And what do you think of the old cadaver?’ His eyes widened and he giggled behind his fingers. ‘That’s what I call Tiberius. Did you see his face?’ he continued. ‘There are bits dropping off. The Gods should call him home, eh?’ Gaius’s eyes gleamed.

Was he mad, I wondered? Or had he taken some juice which stirred his soul and excited his wits.

‘You’ll see such sights here, Parmenon, believe me! I don’t like your companion,’ he continued breathlessly. ‘Sejanus’s turd dropped hot from his anus.’

I stared round the room: it was some sort of writing office with one window overlooking the garden.

‘Oh, don’t worry,’ Caligula reassured me. ‘The cadaver can’t hear us. Right, what did Agrippina say?’

I delivered Domina’s message, and Gaius almost did a jig from foot to foot.

‘Got him! Got him! Got him!’ he murmured.

He danced away, a grotesque sight with his tall, stooping figure and his strange hair, leaping from foot to foot, hands raised like some priest in a trance. He danced back to me.

‘Say it again! Say it again!’

I delivered the full message. Caligula was quick. In spite of his excitement, he’d already memorised it and, opening the door, he pushed me out. Macro was waiting, helmet under his arms. He stretched out his hand. I noticed the bracelet on his wrists, which bore a carving of Castor and Pollux. I had seen a similar one in Agrippina’s chamber. Macro drew me close.

‘You did well there, Parmenon.’

‘How did the Emperor know?’ I gasped.

Macro stepped away, playing with the bracelet.

‘Because he’s a God.’

And, turning on his heel, he led me back to join the Minion, who was in a state of almost nervous collapse: one moment sitting on the marble stone wall bench; the next walking up and down.

‘This has never happened before!’ he whined. ‘Never before!’

I looked round the atrium. Macro had disappeared. The door to Tiberius’s chamber was guarded by two burly German ruffians who stood, shields in one hand, drawn swords in the other. The Minion came up and clapped me on the shoulder.

‘I hope that bitch hasn’t been up to mischief.’

I clicked my tongue and smiled. ‘Don’t be frightened,’ I mocked.

Another hour passed. The doors of the chamber were thrown open and Macro beckoned us forward. We walked in. Tiberius looked as if he hadn’t moved. Gaius was standing beside him, immobile as a statue. We went to kneel before them.

‘Not you!’ Tiberius’s voice grated.

I looked up. Tiberius was gesturing at the Minion. He pointed with his thumb over his shoulder at the garden wall.

‘You certainly know how to lie!’ Tiberius accused. ‘You lied to your Emperor! So, let’s see if you can fly as well!’

And, before the Minion could protest, the two German auxiliaries who had followed us in, grasped him by the arm and dragged him out into the garden. They pulled him to the edge of the parapet and tossed him over. Dreadful screams shattered the silence. Tiberius made himself comfortable on the chair.

‘You see, Macro,’ he joked. ‘I told you he couldn’t fly!’

For a while the Emperor sat in silence as if savouring what had happened. Caligula had stepped back so the Emperor couldn’t see his face, shaking with giggles. The two German mercenaries watched the body fall and then left.

I heard a singing bird trill out its sweet song, and the buzzing of a bee, which surprised me as it was so early in the season. I could only wonder whether I would be next?

‘Kneel back, Parmenon.’

I did so.

‘Look at me! Forget Sejanus’s advice! Look at me!’

I did so. The Emperor studied me closely.

‘Are you a kinsman of Sejanus?’

‘A very distant one, Excellency.’

‘And can you fly, Parmenon?’

‘No, Excellency, I can only swim.’

The Emperor threw his head back in a neighing laugh. ‘Are you a liar, Parmenon?’

‘Excellency, I do not know what the truth is.’

‘Ah, quite the philosopher. Now, Parmenon, relax, you are not going to fly. Just repeat your message.’

Caligula had moved even further back, his face now alert. He shook his head imperceptibly and tapped his cheek. ‘Do not mention me,’ he was saying.

I learnt a lot during that interview. Caligula was acting to survive. He was plotting against the Emperor. Macro, who must have seen his secret gestures, was his accomplice. I repeated the secret message, Agrippina’s last words to me. Tiberius’s face grew livid.

‘Do you know what she means about Drusus?’ he snapped.

‘I don’t understand, Excellency. Drusus is a prisoner in the Palatine.’