Some garden-creators were freedmen of the imperial court, those high-rollers with moneybags for eyes, who always know how to fix themselves up with gorgeous property. Maecenas had been different, born a fabulously rich Etruscan, friend of Augustus and great patron of the arts; he made his garden particularly fine, with libraries and pavilions. This became his retirement home, a setting so elegant that the Emperor Tiberius had lived there for a time.

To enter Maecenas’ Auditorium, as it was called, we passed down a long ramp with a herringbone floor. The monument was built substantially below ground, perhaps as a sunken dining room; when they turned on the water, the inner hall was cooled by a cascade that tumbled down at one end, where deep, white marble steps lined a semi-circular apse. Though never a great socialite, I had been here to a couple of events. The body of the hall can take dining couches, but generally it hosts stand-up soirées with drama, music or readings for well-dressed cultural snobs. Very small appetisers are handed round by blank-faced servers from Gaul in identical uniforms. Flute music nobody listens to wavers over the loud hum of pretentious chatter and rattling jewellery. The ticket price makes you wince.

Though originally a private building, the Auditorium could nowadays be hired, and my father once recklessly shared an evening there with a senator he knew slightly, who wrote epic poetry. Their joint recital was even graced briefly by Domitian, in the happy days when he was only Vespasian’s spare heir; back then he had big dreams but no real expectations of becoming emperor.

Do not ask for a critique of Falco’s writing. I am a loving, loyal daughter.

Today we had it to ourselves, a rather over-elaborate interrogation room. The well-proportioned interior was lined with large wall niches that were beautifully painted with garden scenes and landscapes, all exquisitely done in that endearing Roman style where indoor frescos mimic living plants that you can see simultaneously outside. One end of the hall opened onto a terrace with lovely views towards the Alban Hills. Unfortunately, once Alba became the infamous location of our emperor’s citadel villa, nobody could gaze eastwards without the warped image of Domitian brooding in his fortress, planning ways he could make our lives miserable.

This was an unusually sophisticated venue for an interview with a gangster, but none of Roscius’ violent associates would come looking for him here. If he was overawed by the grand setting, it might work in our favour. He looked around, no doubt hoping to identify statues he could steal, though this was strictly a performance space and no art gallery.

Faustus seemed at home. Did he have an unknown life as an arts connoisseur?

For me, it made a welcome change from barracks and bars. But it would not be my natural choice. The place was too busy making its gorgeous presence felt. I prefer a neutral background for grilling suspects.