Next, Helena wanted to discuss household matters, which meant more meek compliance. My daughters then had an urgent need to show me drawings and ask for new shoes like those their friend three doors down had been given by their spoiling parents. Even the dog stood at the front door with her leash in her mouth.

Only Albia tried to avoid anything to do with me, but I took her out anyway. That would teach her to tell Anacrites she could do an informer’s job.

I was taking the cameo to Petronius. By the time we reached Maia’s apartment, it was so near to evening we only just caught him before he left for duty.

‘Hold on. I want to show you this, off vigiles premises.’

He got the message.

With Albia watching, we inspected the jewel. It was carved from sardonyx, the redder form of onyx. ‘It’s like an agate, Albia—layered hard stone.’

‘More education!’

‘Listen and learn, girl.’

Petronius held the gemstone in his mighty paw while he tried to work out what was going on in the picture. It was a two-layered cut, in low relief. The onyx banding was white and red-brown, beautifully executed. The lower half of the design showed a gloomy bunch of captured barbarians. On an upper frieze, gathered around twirly horns of plenty, minor deities were applying triumphal crowns to the noble brows of bare-chested noble personages. An eagle, probably representing Jove, was trying to muscle in. ‘Claudian imperial family,’ Petronius guessed. ‘They always have that clean-cut, very close-shaven look. They were all untrustworthy midgets really.’

Albia giggled.

‘He’s exaggerating, Albia. Lucius Petronius, being a great hulk himself, likes to make out anyone dainty is deformed. However, this is so special it may even have belonged to Augustus or someone in that family, either commissioned by them or given as a gift by a sycophant.’

Petro’s eyebrows shot up. ‘It’s that good?’

‘Trust me; I’m an antique dealer. Without provenance it’s hard to be sure, but I would say this could be the work of Dioscurides. If not his own piece, it certainly came from his workshop.’

‘Dio who?’

‘Augustus’ favourite cameo-cutter. Well, look at the workmanship! Whoever carved this was brilliant.’

Petronius leaned towards Albia and growled, ‘Have you noticed how Falco keeps sounding like a bent auctioneer these days?’

‘Yes, at home we all feel we are living with a fake-wine-jug seller.’

‘Rag away!’ I grinned. ‘Whoever owned this—I don’t mean some mystery lodger at the spy’s house—knew its worth. The purchaser, who may have been a woman because it has been a necklace pendant, had the money and the knowledge to buy real quality.’

‘Someone in mind?’ asked Petro.