On a good day, Titianus would have been off duty. I would have pressed his disloyal colleagues to give their opinion of his half-baked Aviola inquiry, and they might have dished dirt. It was not a good day. Instead of working at night, like any conscientious investigator who goes out on foot with the troops, this swine liked to take his ease on the day shift, playing with paperwork by himself. He was available in his snug.

I could see why the Second Cohort had made Titianus their inquiry officer. He would never meld in anywhere else. The average firefighter is built like a stone sarcophagus, with short wide legs and no neck: a wide-loom tunic man. They like ripping those tunics off in public, to amaze onlookers with their physique.

Sadly for him, Titianus had hair of an indiscriminate colour, pouchy eyes and a desolate expression, while his physique was far from fantastic. He did wear a tunic that was wider than it was long, but it hung off him in folds. It looked like the skin of an obese patient whose doctor has starved him into losing two hundred pounds, the week before he collapses and dies of malnutrition. (‘At least he was healthy when he passed away.’ ‘Well, thank you, doctor!’)

Unlike normal inquiry officers, we found Titianus sitting up straight at his desk. Evidently he had not been shown how to put up his boots on the table while he cleaned out his ear-wax. What was wrong with the Second Cohort’s training manual? Finding him not belching over a packet of cold bar snacks, Uncle Quintus looked disappointed. He is always hungry and was expecting to pinch nibbles.

After introductions, Quintus left me to it; he wandered back outside to the exercise yard, the hub of any vigiles barracks, where men on call were tidying equipment. I knew he would start asking questions about firefighting kit, then while he endeared himself to the troops by treating them as human, he would fish for any facts that Titianus might prefer to keep from us.

In the office, I started by asking the dolorous-eyed Titianus about the night of the robbery. There were no surprises. That in itself was no surprise.

‘Yes, it all fits!’ He probably thought my remark was a commendation. ‘One thing you can tell me, Titianus, is what the killers used to strangle the victims. Rope has been mentioned. Is it correct you took it away as evidence?’

This time Titianus squirmed unhappily. ‘There was a rope, left around the dead woman’s neck. That steward, Poly-wotsit, took it off her – act of respect to the dead. I didn’t collect it from the scene immediately as I was too busy, and later it had vanished. Thrown out when they tidied up? It wasn’t important.’

‘It might be. An aggressive lawyer may call this carelessness,’ I warned him frankly.