‘You dress your hair,’ I replied. ‘You put paint on your face and bathe your body in perfume. You wear the most elegant robes and always arrange for Cassius to sit near you when we eat. You are not trying to seduce him, are you?’

‘Oh, I’ve already done that,’ Agrippina murmured. ‘Last night.’

I recalled Agrippina leaving the evening meal early, complaining she felt unwell, the usual sign that she wished to be left alone. Chaerea had retired an hour later.

‘I didn’t think you’d be so stupid!’ I retorted.

‘What’s Cassius going to say?’ Agrippina snapped. ‘That he dared seduce the Emperor’s disgraced sister? I know every mark on that beautiful body. More importantly, I have found a man who hates Caligula even more than I do. Do you think the army liked that stupid spectacle on the coast, escorting carts back into Rome full of seashells?’

‘That doesn’t make Chaerea a traitor,’ I replied.

‘Oh, Parmenon, think back to last night and the other times we’ve talked with Cassius. Every time I mention Caligula he blushes slightly. I discovered why: Caligula calls Cassius a girl. One of Chaerea’s tasks is to ask the Emperor every day for the personal password.’ Agrippina bit back her laughter. ‘Caligula teases him with replies such as “Vagina”, “Penis” or “Kiss Me Quick”. Can you imagine the roars of laughter which greet this? Cassius also tells me that others hate Caligula just as much as he.’ She tapped me on the hand. ‘Now, for practical news. My husband Domitius has done us all a favour by dying of dropsy. I won’t be a hypocrite — I didn’t give his life a passing thought, so why should I mourn his death?’

‘And your son?’ I demanded.

‘A bouncing boy with red curls. He’s already ordering about the other children in the nursery.’

‘And?’ I demanded. ‘There is something else?’

‘Cassius has brought a pass. You can return to Rome for the winter. I think Caligula wants to find out how his sister is faring. When Cassius leaves, you are to go with him.’

‘To plot, be caught and executed!’ I exclaimed.

‘No, listen.’

Agrippina gripped my wrist, a sign that she was going to impart something important. It always made me shiver, reminding me how Charicles used to take Tiberius’s pulse.

‘Caligula will die,’ Agrippina insisted. ‘And who is there left? Those doddering fools in the Senate may try and restore the Republic but the army won’t allow that.’

‘Your Uncle Claudius?’ I replied.

‘Precisely.’ Agrippina squeezed my wrist even tighter. ‘If Caligula dies suddenly, there’ll be confusion. You and Cassius must ensure that Claudius is hailed as Emperor. He’ll bring me back to Rome.’

Agrippina dropped my wrist. ‘Whatever happens, Parmenon, you must ensure that, somehow, Claudius is brought forward. Naturally, in the chaos following Caligula’s death, my son must be closely protected.’ She got to her feet and pulled me up. ‘By the way, I know you’ve got too tender a heart so Cassius will do this for me — ensure that Caligula’s wife Caesonia and her little brat don’t survive any longer than he does. Now, come! I am sure Cassius is already pining for me and we’ve got preparations to make.’

It was good to be back in Rome. Despite the winter, the taverns were crowded as usual. After the silence of Pontia, I enjoyed walking through the different quarters watching the barbers shave their customers in the middle of the street, the loud-mouthed hawkers selling their small boxes of sulphur matches and trinkets, the raucous cries of the sausage-sellers with their makeshift mobile ovens. Schoolmasters, ringed by their pupils in a small, dirty square, shouted themselves hoarse. Nearby, a money-changer sifted his coins in a metal grille whilst his assistant pounded with a shiny mallet on clipped and chipped coins. Conjurors and tricksters swarmed everywhere, competing with the beggars. The sheer frenetic bustle of their lives was a sharp contrast to the horrors of Caligula’s court or Agrippina’s seething anger as she plotted her return.

I lodged with Cassius Chaerea in the Praetorian barracks near the Viminial Gate. Of course, I had to be presented to the Emperor, and was obliged to attend one of his famous supper parties in Livia’s old palace. Caligula was, as usual, lounging on a couch. He seemed taller and thinner, his face had assumed a skull-like look, hollow-eyed and sunken-cheeked. He was nearly bald except for an incongruous tuft of hair which rested on the nape of his neck. He looked me up and down. I was obliged to kneel and kiss his slippered foot.

‘How is my darling sister?’ he lisped. ‘I often think of her.’ He repeated his ominous threat, ‘And, when you return, Parmenon, remind her I have daggers as well as islands!’

Chaerea had informed me that Caligula had banished many of his enemies and, on a mere whim, sent executioners to hunt them down and forced them to take their own lives. If they refused, they were cruelly butchered.

‘Well, get up! Get up!’ Caligula waved his hand airily. ‘I have to retire.’

I took my place on the couches which were arranged in a horseshoe around the Emperor’s which stood on a raised dais. The mood was one of sheer terror. No one dared eat without the Emperor’s permission and everyone was petrified of catching his eye. The Emperor withdrew, and when he returned, he was dressed as a woman in a beautiful silk gown, with a veil over his balding head. He wore artificial green finger- and toenails. He didn’t take a seat but clapped his hands and the musicians struck up the tune of a well-known Syracusan dance. The Gods be my witness, we had to sit and watch as the Emperor of Rome danced and cavorted as if he were a tumbler from Antioch. Of course, at the end, the applause was deafening. Caligula, still in his female clothes, returned to his couch, sharing it with an actor who was under strict instructions to treat the Emperor as if he was a woman.

I was forced to remain in court for the next few days. The Emperor lived in a world of his own. He often made public appearances in a woman’s cloak covered with embroidery and precious stones. Or, in sharp contrast, he’d wear the famous military boots which gave him his nick-name. He had an artificial golden beard which he would fasten to his face and carry a thunder-bolt trident or serpentine staff as he pretended to be Jupiter or Apollo. On occasions he’d disport himself as Venus, which was truly dangerous: with his bony shoulders and spindly legs, it was difficult not to laugh out loud.

Caligula’s only link with sanity seemed to be his love of chariot racing but even here his madness had eventually manifested itself. He fell in love with his own horse Incitatus and built him a marble stable with an ivory stall, purple blankets and jewelled harness. Before a race the entire neighbourhood around the imperial stable was put under armed guard, and sentence of death was passed on anyone who disturbed his horse. The charioteers were divided into different factions, with an intense rivalry between the ‘Blues’ and ‘Greens’. Caligula supported the ‘Greens’. Woe betide any charioteer from an opposing faction who threatened the Emperor’s favourites — they could expect either themselves, or their horses, to be poisoned. No wonder Rome seethed with unrest.

At first I was left alone by the conspirators. Caligula had me watched but, as the New Year came and went, dismissed me as a nonentity; he was more interested in the games and festivities planned for the end of the month. I was left to my own devices. I went out to the Via Sacre and visited the baby Nero. He was, as Agrippina had described him, a bouncing, unruly, little boy with bulbous blue eyes and a shock of red-coppery hair. Even then he was a born actor. I had to sit with his guardians while the little fellow sang and danced. I don’t believe in premonitions, yet, as I watched the child, I kept thinking of the monster on the Palatine. For the first time in my life, I quietly prayed that Agrippina had chosen the right course for her son. The aged aunt who looked after the boy was a cold, austere, old woman with a face like vinegar.