The principals were missing, the reviews have been awful, but the plot was promising enough to hold its audience yesterday as the curtain went up on the autumn's new production at Holyrood. On show: the SNP's plans for a local income tax, which has already gone down like a lead balloon with businessmen, trades unionists, accountants and leader writers across the country. “Dire” “unworkable” “rush to miss it” are just some of the more printable comments hurled from the stalls.

Cathy Jamieson, standing in for whoever is meant to be playing the lead in Labour's own melodrama, wanted to know why the tax plans had not been cancelled as soon as they had gone out for rehearsal or “consultation” as the critics put it. After all, she said, what is the point of a consultation if you don't listen to those you have consulted?

To which “Ha!” would have been a good response. Coming from Labour, which invented the whole concept of phoney consultations, that was rich indeed. But Nicola Sturgeon, standing in for the absent star Alex Salmond, preferred to argue that the reviews had not been as bad as that. She pointed instead to those who had labelled the local income tax “fair” and “progressive” while the tired old council tax which Labour had been staging for years, like an outdated production of The Mousetrap, was “unfair” and “regressive.” As for consultations, the biggest of the lot had been conducted at last year's elections which had run down the curtain on Labour to a sustained chorus of booing. “Now that's the kind of consultation I like,” she quipped.

So far so predictable. But then an element of pantomime crept in when Ms Jamieson produced a classic villain in the shape of Mrs Thatcher. “We know that Alex Salmond is a devotee of Margaret Thatcher's economic policies,” she sneered, “now we see that he is also a devotee of her tax tactics.”

“Oh no he's not,” snapped Ms Sturgeon. Or rather, what she actually did was to quote Gordon Brown as saying: “Margaret Thatcher saw the need for change. I admire her. She is is a conviction politician, I am a conviction politician just like her.”

It is dialogue like this that should have had the director reaching for his blue pencil, but the audience loved it. Quoting Mrs Thatcher or Gordon Brown at Holyrood these days is an instant excuse for uproar from the claques in the balcony. No one quite knows why. It's just one of those things.

Meanwhile Annabel Goldie came out with a somewhat garbled line about how the problem with taxes is that no one likes paying them, which, as Ms Sturgeon observed, was such a stunningly obvious remark that it might have been better to reject the script altogether.

All of which paved the way for the eagerly-waited new matinée idol, Tavish Scott, the Liberal Democrat leader. High in the VIP gallery, the seats were crowded with his acolytes, Liberal Democrat peers and assorted grandees of the party. We awaited a dramatic entry.

The problem was that he had decided to try out a completely new part - something to do with wind turbines in Cambeltown. Now there may be an argument for this experimental type of drama, but frankly we prefer the tried and tested. Let's hope he gets some better material next time around.