The villa had been in the family of Acilius Glabrio for generations. Palatial, and surrounded by the wide gardens that still bore the name of their original designer, it was one of the most splendid houses in Rome – a statement of wealth and status. Yet its history was tragic. Messallina, the wife of the Emperor Claudius, had coveted the gardens, and forced their owner to suicide. Later, her infidelities exposed, it was here she had taken her own life. The property, Volusianus thought, would bring Acilius Glabrio no better fortune.

The growth of a conspiracy was much like that of a plant. At first there was little to be done but carefully observe the tendrils it put out. But there came a time when it must be cut down, its roots grubbed out. Inside the shuttered residence Acilius Glabrio was in treasonous conclave with another disaffected senator and two junior officers, one a Praetorian, the other serving with the Horse Guards. Volusianus was not overly concerned by the disloyal senators. Their kind talked and talked. Even when they finally acted, it was seldom with proficiency. But the involvement of the military demanded decisive measures.

After a month of prevarication, Acilius Glabrio had heeded the poetic advice of the usurper over the Alps. When he tampered with the loyalty of the troops, he had drawn the sword. It was typical patrician arrogance, Volusianus thought, that Acilius Glabrio had not been deterred by the disappearance of the man who had brought the message from Postumus.

A light flashed on the wall of one of the rear courtyards of the villa. The shuttered lantern opened three times. Volusianus heard Murena quietly give the orders. The complex was ringed with troops. Now, above the sussuration of the wind in the trees, came the distinctive sounds of armed men moving into position at the front and rear gates.

It was what every member of the senate feared – the arrival of the Praetorians in the dead of night. But the soldiers approaching the entrances were a diversion. It would take time for the gates to be opened, time in which much incriminating evidence might be destroyed.

‘Open in the name of Gallienus Augustus!’

The command was followed by a series of heavy blows to the front gate. Moments later, the commotion was repeated at the back gate.

Volusianus started walking to where the light had shown. Murena and three Praetorians followed at his heels.

At the foot of the wall Volusianus softly called the password: Iustitia.

A pale circle of a face peered over. Then a rope ladder coiled down. Volusianus sent Murena and the Praetorians up first. He had not lived to his advanced age by taking unnecessary risks.

It was difficult climbing in a mail shirt. Volusianus discarded his cloak to prevent being further encumbered.