Matthew Norman: Thank you, Sir Thomas. Six of the best is just what they needed

The dunces who are our MPs still cannot grasp that they have been naughty

Try to forgive this lurch into the solipsistic confessional box more happily occupied by the likes of Liz Jones, please, but last night we had one of those excruciating showdowns that tend to afflict couples long manacled together by the unflinching bonds of holy wedlock.

"We need to talk," I murmured, pouring her a Goliathan gin and tonic, and gulping down my tumbler of Havana Club rum. I still love you to bits, I went on, leaning over to push a couple of potential missiles out of her reach, and hand on heart I always will. But there's someone else. "I've, err... Look, this isn't easy. I've, um. I've fallen..."

"You've fallen in love with Thomas Legg?" she interrupted. "I presume it's Sir Thomas Legg?" I nodded meekly. "Oh, that's fine," she said, "so have I. For God's sake, who hasn't?"

Who, with a few hundred obvious exceptions, indeed? Who could gaze for a moment upon that noble visage and not fantasise about nuzzling his neck, stroking the straggly remnants of his hair, and whispering, "I adore you, Leggy, and I want to have your babies" into one, if not both, of his ears?

In that face lies a potent echo of Richard Wattis, the character actor who personified the faintly bemused, world-weary, buck-passing civil servant in endearingly amateurish British movies long ago. I'm sure this is why Gordon Brown picked him to audit the expenses of honourable members. Somewhere bubbling away in his subconscious was the memory of Manton Bassett, Wattis's Department of Education bod in The Belles of St Trinian's, who went off to sort out the miscreants; but who, in celluloid's first and grittiest depiction of Stockholm Syndrome, was taken hostage before going native and ending up as the girls' accomplice.

You can't really blame Gordon for the misjudgement, even if scores of the Labour MPs who barracked him at a meeting this week are doing just that. The Prime Minister had sound reason to anticipate the ritual whitewash, not least because Sir T has a bit of form in this area. The 1988 report he co-wrote on Sandline International's sale of arms to the exiled government of Sierra Leone, and our government's involvement in that, was a classic of its kind. Lord Hutton could have applied the Dulux brilliant gloss with no more élan.

But the thing about these mandarins is, you want them when they're young, in career terms, and ambitious. Gordon's error was hiring a 74-year-old, retired from Whitehall and with a reputational score to settle over Sandline. So it is that this gentle, parfait knight has given the expenses story its second act. Far from being seduced by global democracy's answer to St Trinian's, he has stormed into assembly and summoned not only the fourth and fifth formers but the prefects as well to his study for six of the best. Or in the case of the headmaster, side-splittingly enough, £12,415 of the best for overclaiming on cleaning, gardening, laundry and decorating. That Gordon Brown should be the largest repayer so far (we may expect demands many times larger once Sir Tom gets round to the Capital Gains flippers) is but one of the hilarities on offer at Westminster this week.

The general amusement surrounds the cloud of bewilderment that months of stormy public outrage have failed to dispel. Wondrously, these dunces still cannot grasp that they've been naughty and retain quasi religious faith that they can bluster the issue into oblivion. What they were doing all summer defeats me, but I'm bleeding sure they weren't doing the rounds of their constituents' doorsteps to gauge the public mood.

Take Jacqui Smith, as Max Miller would have invited us. Her faux apology brings to mind Shaggy's single "It Wasn't Me", in which a guy whose girlfriend walks in to find him in flagrante with the neighbour continues to insist, with heroic futility, that it was indeed not him:

"But she caught me on the counter (It wasn't me)

Saw me bangin' on the sofa (It wasn't me)

I even had her in the shower (It wasn't me)

She even caught me on camera (It wasn't me).

She saw the marks on my shoulder (It wasn't me)

Heard the words that I told her (It wasn't me)

Heard the scream get louder (It wasn't me)"

It was Jacqui, of course, as the coppers who guarded her sister's front door have confirmed by giving a different account of the number of nights she spent in town. That'll learn her, albeit a little late, not to pick pay-rise fights with the Police Federation.

Most delicious of all, meanwhile, is the introduction into the debate of a concept that those raising it have treated with contempt these past dozen years and more. Many MPs have pointed out that my darling Tom-Tom has navigated the ship of state towards a grave breach of "natural justice" by retroactively imposing expenses limits of the kind that have cost Gordon a dash over 12 large. Ann Widdecombe, fabled defender of handcuffing hospitalised prisoners, is but one to wheel out this fuddy-duddy notion.

And she's right. Technically, it is a blatant breach of natural justice. Then again, it is an affront to natural justice to remove the right to silence and trial by jury, kick habeas corpus in the cobblers by extending the period of detention without charge to almost a month, and store the DNA material of the innocent on a database. I'm no expert on jurisprudence, or indeed on anything else, but some will regard these as marginally more serious than making a bunch of petty crooks return what they've half inched from Johnny and Joanna Tax-Payer.

Now heaven loveth a sinner that repenteth, and hats off to heaven for that. Here on earth, alas, it isn't so easy to loveth those who pliantly voted all that crap on to the statute books – or in the case of giving the Inland Revenue powers to send Stalin's secret police into orgasm, never voted for them at all; and never complained about that wicked violation of democratic principle.

What my Tommy, a lawyer by training, is saying is what Mr Tony Blair, Gordon, David Blunkett, Jack Straw, Shaggy Smith and the rest implicitly said when they were butchering natural justice: that sometimes the concept can be trumped. But where their trump cards were expediency, authoritarianism and sucking up to the right-wing media, Leggy's ace of spades is plain morality. It doesn't matter what the rules failed to spell out, or what the weedy rubber-stampers of the Fees Office were bullied into agreeing. All that counts is that it was plain wrong, and that any reasonable person on the Clapham bendy bus would have known it.

What we are seeing again from the Muthah of Parliaments, in this gentler second act, is pure and simple amorality. As a comic device, that's always a winner. Who doesn't have a soft spot for those anarchic gymslip terrors? Here in what loosely passes for the real world, however, we don't want Compton Basset joining them in the Great St Trinian's Train Robbery. We want him to come over all Jimmy Edwards and unleash his cane. This is precisely what my Tommy has done, and will continue to do, and why he is welcome to make it a ménage a trois in Shepherds Bush any time he likes.