David Prosser: The reprieve for Messrs Thiam and McGrath may only be temporary

Outlook Better than expected financial performance, a dividend hike and a reduction in the bill for the aborted purchase of AIG's Asian assets. Surely Prudential's management have done enough to silence those investors who have been calling for their heads since the humiliating failure to seal the AIG deal?

Maybe. Certainly, the insurer's most vocal critics in recent months were conspicuous by their absence following yesterday's results announcement. Just three months ago, the likes of Neptune Investment Management's Robin Geffen were demanding the resignations of Tidjane Thiam and Harvey McGrath, Pru's chief executive and chairman. Once the insurer posted its numbers, not a peep was heard from them.

And yet. The bigger question about the AIA debacle remains as valid now as it did in the days following the deal's collapse. Having fought so hard to persuade investors that AIA was critical to Pru's strategy of turning its Asian operations into the main driver of growth at the business, are Messrs Thiam and McGrath credible when they now say they can achieve a step-change in Asia even without the acquisition?

It is not just that Pru's Asian business will now scale upwards much more slowly. Having escaped Pru's clutches, AIA is now pursuing an IPO and has appointed the ambitious and formidable Mark Tucker at its chief executive. It will be a major competitor for Pru in the region. It might even find itself in a position to reopen talks with Pru, but this time with AIA as the bidder for the British company's operation.

As long as these anxieties persist, Pru will remain under pressure from some shareholders for a sacrificial lamb. In which case, either Mr Thiam or Mr McGrath may yet have to fall on their sword.

If so, which one should go? Well, the case against Mr Thiam is strong. This was his deal from the outset, and his second misjudgement in a very short tenure at the top of the company (he had already had to be talked out of taking a non-executive directorship at Société Générale).

That said, it is difficult to imagine who would replace him – certainly no one springs to mind from the insurance sector with Mr Thiam's creative dynamism. And with the battle in Asia to come, Pru needs a chief executive who doesn't need six months to a year getting up to speed.

That leaves Mr McGrath. Pru's chairman should not have allowed his inexperienced chief executive so much rope. Reining in over-ambitious young Turks is precisely what chairmen of Mr McGrath's pedigree are paid to do. In other words, he is just as culpable for AIA. He is also more expendable.