Well, that was enlightening.

It was inevitable that Ed Miliband would go on HSBC, tax evasion, Tory donors and Lord Green.

It was equally inevitable that David Cameron would shout until he was hoarse about Labour’s record on tackling evasion, Ed Balls tenure as City Minister and Labour’s reliance on trade union funding.

On days like this, it is painfully clear that the objective of both leaders is not to engage in reasoned, rational debate. Nor is it really even to ‘win’ the overall exchanges in the chamber. Their objective is simple: get the best sound bite they can on the package on the evening news bulletins.

Having both shouted a few suitably outraged lines, they can regard it as ‘job done’ and move on. David Cameron may be a little the more satisfied of the two, having mounted an assured enough rebuttal to prevent Ed Miliband securing the rout he may have felt was his for the taking.

But I don’t expect that Miliband will be too unhappy with his 5 minutes’ work either. He knows that the emerging narrative is ‘Tory links to tax evasion’ and he stoked that fire effectively.

This current saga has more distance to run and it remains unclear whether it will have any significant bearing on either party’s standing in the polls. On the face of it, it seems to fit Labour’s message that the Tories are too close to big business to effect the real reform required to create a more ‘responsible capitalism’. But early polling on the matter suggests that the public rates Labour’s ability to tackle tax evasion only marginally more favourably than they evaluate the current government’s record.

To a general public that is unlikely to engage in any great detail on the specifics of the case and who knew what when, there will be a strong tendency to file this under ‘they’re all as bad as each other’.

The emergence of this row at this particular time may yield one advantage for Labour, however. Having spent much of the last week since Ed Balls’ forgetful appearance on Newsnight trying to satisfactorily answer the question ‘So who are your friends in the business community?’, Labour will be glad of the chance to shift the debate towards ‘So let’s look at your friends in the business community.’

Viewed in this context, a lack of big-business backers may not be quite the hindrance it was portrayed as this time last week. Ed Miliband was glad to point out at PMQs today that none of those named in the HSBC files has donated to Labour “on my watch”.

Overall this was another PMQs to be watched mainly as a form of punishment. It was predictable, ill-tempered and shed little light on a complex situation. If you haven’t already, get used to that between now and the election.