It is, of course, a crime for any of us to profiteer while on foreign service; commit parricide; rape a vestal virgin; conspire to assassinate the Emperor; fornicate with another man's slave; or let amphorae drop off our balconies so as to dent fellow citizens' heads. For such evil deeds we can be prosecuted by any righteous free man who is prepared to pay a barrister. We can be invited before a praetor for an embarrassing discussion. If the praetor hates our face, or merely disbelieves our story, we can be sent to trial, and if the jury hates us too we can be convicted. For the worst crimes we can be sentenced to a short social meeting with the public strangler. But, freedom being an inalienable and perpetual state, we cannot be made to endure imprisonment. So while the public strangler is looking up a blank date in his calender, we can wave him goodbye.

In the days of Sulla so many criminals were skipping punishment, and it was obviously so cheap to operate, that finally the law enshrined this neat dictum: no Roman citizen who was sentenced to the death penalty might be arrested, even after the verdict, until he had been given time to depart. It was my right; it was Petro's right; and it was the right of the murderous Balbinus Pius to pack a few bags, assume a smug grin, and flee.

The point is supposed to be that living outside the Empire is, for a citizen, a penalty as savage as death. Balbinus must be quaking. Whoever thought that one up was not a travelling man. I had been outside the Empire, so my verdict was not quite that of a jurist. Outside the Empire can be perfectly liveable. Like anywhere, all you need to survive comfortably is slightly more cash than the natives. The sort of criminals who can afford the fare in the first place need have no qualms.

So here we were. Petronius Longus had convicted this mobster of heinous crimes and placed him under sentence of death – but he was not allowed to apply a manacle.