‘He’s sleeping with her, isn’t he?’

‘I didn’t hear that!’ Agrippina sat as immobile as a statue.

‘Domina,’ I replied. ‘If you don’t hear it from me, you’ll hear it from others. The Emperor is sleeping with his own sister. Is that the price you paid?’

‘I had no choice,’ Agrippina replied softly. ‘He needs Drusilla.’ She glanced at me. ‘We are all demons, Parmenon. And can you blame us, brought up in the shadow of Tiberius’s bloody hand? You never met Livia, Tiberius’s mother! One day with her would chill your soul.’

‘Did you encourage him?’ I asked.

‘Encourage him! Encourage him!’ She glared at me. ‘Do you think I like this, Parmenon?’ she whispered. ‘Did I ask to be born into the purple? Did I ask to be raised by someone like Livia? To depend, for every breath of my life, on men like Tiberius and Sejanus? To be given to that drunken oaf Domitius in marriage! To be terrified,’ — she touched her belly — ‘of becoming pregnant lest a demon like Tiberius whip the child away from me! To have a brother like Caligula? To have my mother starved to death, and my brother reduced to eating the straw out of his mattress?’ She sprang to her feet, rubbing her arms as if cold. ‘Caligula has been sleeping with Drusilla since they were children. They used to clutch each other at night like terrified little rabbits. I tried to stop them, and so did my aunt. Mother suspected but. .’ She shook her head. ‘If Drusilla can keep him sane, then let him have what he wants. After all, the Pharaohs of Egypt married their half-sisters.’ She glanced over her shoulder at me. ‘Anyway, what do you advise, Parmenon?’ she asked sardonically. ‘That I give him a lecture on morality? Find him a new wife? What?’ She stamped her foot. ‘What can I do? Separate them? Caligula would take my head. What have you become, Parmenon? A stoic? A philosopher? Weren’t you there when Tiberius died?’

She held out her hand which I grasped. She squeezed mine and let go.

‘Who advises him?’ I asked.

‘Macro and myself.’

‘And Drusilla?’

‘Drusilla has a pretty face and an empty head. She’s as vacuous as she’s beautiful.’

‘Are you giving Caligula drugs?’ I asked.

‘You know I am: valerian seed to soothe the nerves and help him sleep.’

I stared across the garden. The morning mist was lifting. I heard the clink of metal, the rumble of carts as they were brought out onto the cobbles for the luggage to be stowed. I felt sorry for attacking Agrippina. The imperial court was not a place for morality, just for power and survival.

‘If the Senate find out,’ I replied slowly, ‘the Emperor’s relationship with his sister could be fanned into a scandal by that gaggle of hypocrites in Rome. They’ll start accusing him of being degenerate. He has the blood of Mark Anthony in him. They’ll gossip about his ancestor’s love for Egyptian ways. .’

‘So?’ Agrippina demanded.

‘If he is to honour one sister,’ I continued, ‘then let him publicly honour all three.’ I laughed. ‘You’d like that anyway. Let there be no distinction between his love for all his sisters. It will cloud people’s minds, blunt suspicion.’

Agrippina seized my hand again, gripped it and walked away.

Whatever Agrippina had done with Macro’s help, it certainly worked. If anything, Caligula appeared saner than any of them. He entered Rome with the approbation of both Senate and people. He was greeted by the College of Priests and the Vestal Virgins. Glory and honours were bestowed on him. Caligula acted with all the gravitas of Augustus. He refused to have the dead Tiberius criticised and had his ashes solemnly interred in the imperial mausoleum. He stood at the rostrum of the Senate and said he needed their help in ruling. He decreed an end to the treason laws, issued pardons and had the secret police records burnt in the Forum. He brought the ashes of his dead relatives back for honourable burial and promised a period of reconciliation. I was dumb-founded, but everybody was pleased. Caligula had spent the last few years on Capri, and very few people really knew the true nature of the monster they had taken to their bosom. He opened the treasury and lavished rewards on the Praetorian Guard and the legions. Informers and spies were driven from Rome. At banquets and festivals he acted with the utmost propriety.

It was all a charade, of course. I sometimes caught him watching himself in the mirror, practising gestures and still talking to that mysterious, invisible presence behind him.

Despite my forebodings, Agrippina seemed more relaxed. She moved back with her husband Domitius to his mansion on the Via Sacra. He soon began to display the symptoms of dropsy, but Agrippina didn’t seem to care. When I questioned her, she pulled a sorrowful face.

‘Domitius has brought his own death upon him,’ she murmured. ‘I did not ask him to be my husband or to be a drunken lecher, and boorish both in bed and at table. Like a lot of people, Parmenon, he should be careful what he eats and drinks and whose bed he shares.’ She tapped her belly. ‘I have my son: Domitius is no longer needed.’ She changed the subject and refused to discuss the matter any further.

Pregnancy suited Agrippina. She positively bloomed and, as her belly grew bigger with the monster within, she fought to control the monster without. Despite a few mistakes, Caligula maintained his mask and behaved himself. He liked to process in triumph through the city showing himself to be magnanimous and merciful. On one occasion, at a banquet, he stared into a lucent pool of water as if he was concentrating on a mirror.

‘I forgive you,’ he murmured, lifting his hand, talking to his own reflection. ‘I, the Emperor, pardon you!’

He raised his head, eyes half closed, and pretended to be a second Augustus listening attentively to speeches or poetry. The mob loved his grandiose gestures, especially when he staged games in the amphitheatre near the Campus Martius which resulted in the killing of four hundred Libyan lions and an equal number of bears. Agrippina fought to keep him in line. Her two sisters, Julia and Drusilla, were married off: the favourite to Lepidus, a man whom Caligula had also slept with. Caligula’s first wife had died when he was on Capri. He married again but soon divorced his next wife. He only had eyes and heart for Drusilla. Lepidus, I suppose, was to act as panderer to the bedroom and head off any scurrilous gossip about the Emperor and his sister. When he wasn’t closeted with Drusilla, Caligula pawed and kissed two actors, Mnester and Pallas.

Agrippina watched her brother closely. She made sure he did not drink too much at banquets or leap up to join in the singing and dancing. She relied for help in controlling him on two other people: Caligula’s aged aunt, Antonia, and her son, Claudius. I’ve never really been able to decide whether Claudius was a great fool or a very wise man. Slack-jawed and vacuous-eyed when he talked, Claudius sounded as if he suffered from a stroke. He spat and stuttered as if his tongue was too big for his mouth and, when he walked, dragged his foot behind him. Clumsy in all his movements, Claudius’s table manners were no better. He’d gobble his food and slurp his wine. He became known as Claudius the Windbreaker or Claudius the Farter because of his offensive personal habits. Nevertheless, he was a great scholar of the history of the Julio-Claudian House and Caligula would humour him by listening to his droning speeches. Claudius appeared more and more in public, and Caligula even made him Co-Consul, an act of magnamity and clemency which endeared him to the Senate and the powerful ones of Rome.