The Lost World of Michael Bywater: Friends, Romans, countrymen...

Blame Sulla. Beaky nose, sneaky look in the eye, weak chin, bit of a Herbert you'd have thought, to look at him on a coin. None of us look our best on a coin, it's true, but if your daughter had brought him home you'd have not been pleased.

Old family, but that was it. Poor as temple mice, my dears. But not for long. Where he got the money from, nobody knows. Talk of inheritances. Distant cousins. Does anyone believe in distant cousins? Distant cousins means no good, undeclared income, unmarked notes, underneath the arches, no questions asked.

But he got it. Gathered together a fat enough wad to turn himself into a Senator. By 109BC he was quaestor to Gaius Marius, who was running the war against the Numidians. Good going. Not unlike Mark Thatcher turning up as a field marshal, except less, let's be frank, common.

Here's a bit of Latin: dictator rei gerendae causa. Means "dictator during the matter in hand". Being dictator overrode the major principle of collegiality in the Republic of Rome: you didn't have one man in charge of anything. For extraordinary reasons, though, or in extraordinary times, you might suspend that principle for up to six months, or for however long the war lasted, whichever was the shorter.

Whichever was the shorter.

And the Roman Republic didn't even particularly like that. After the Second Punic War, they outlawed the office of dictator altogether, instead granting extraordinary powers to the two current consuls. Checks and balances. Good thinking.

But here comes Sulla, fallen out with Gaius Marius and marching on Rome. Gets himself appointed to a new dictatorship, one he invented for himself: rei publicae constituendae causa - "for the reconstituting of the republic". Same thing, but no time limit. Times of perpetual emergency, do you see? Can't tell when Johnny Enemy may strike, or where, or whence. Johnny Enemy may be within or without. May be moving among us as we speak. May be sneaking across the borders. Action needs to be taken. Normal procedures suspended. Things back to normal as soon as threat dies down. Can't tell when that will be. The innocent have nothing to fear. National security. Intelligence. Briefings. No weapons of mass destruction, but if there had been, Johnny Enemy would have had them. Powers, you see. That's the answer: special powers. First it's rei gerendae, then it's rei publicae constituendae, and, fiddle how you like, powers, once invented, are seldom willingly resigned.

You'll not want to be insulted with the old saw about the lessons of history, but this is an old one and perhaps needs dusting off. There was a direct line - albeit with a couple of retreats, not least Mark Anthony's lex Antonia which lay (how ironically) between Julius Caesar and the Augustus - from Sulla to the raft of emperors which followed, one after another, until Rome both ex- and im-ploded, and hello to the Dark Age.

Special powers. And the thing about special powers is they cease to be special (times of war! constitutional crisis! the enemy at the gates! the enemy within! the Axis of Evil!) but remain as powers. The process, like some grim fractal of imperium, runs at every level. When did any government last repeal a law, except to replace it with further, more draconian ones? Each of them little laws, pissant laws, laws of no importance except (exceptional circumstances!) they are laws, and they simultaneously require and legitimize the extended application of power. And it's a short step from laws about no rare hamburgers and no fireworks to laws about identity cards and imprisonment without trial.

A few weeks ago I was, I think, a republican. But it was the great Roman Republic which fell prey to dictatorship. This week I was talking about it to some policemen and I realised that the police and armed forces' oath of loyalty to the monarch was a great guarantee, in the end, of freedom: that they will say "We do not have to do what the Government says because our oath is not to them."

Briefly, I felt relieved. Until one of the policemen said, "Yes; but it's moving. It's moving all the time. And you know where it's moving to? The Home Secretary." Times of danger. Invisible enemies. Special circumstances. Special powers. And why not? It's worked before. Blame Sulla. But watch your back.