The ScotAm board has to choose between the Pru, Abbey National and the Australian-based AMP by the end of the month. Analysts said a decision is unlikely to be announced on Good Friday, the Easter weekend or Easter Monday.
It is now clear that the initial decision will only name the preferred bidder. Unless the other bidders give permission details of the rival offers will not be published until the ScotAm board's formal circular is sent to members for approval, and that could be up to two weeks after the initial announcement.
That opens up the possibility of an argument over whether the best bid has been chosen.
ScotAm's advisers, SBC Warburg, have continued to insist that the winning bidder may not necessarily be the one with the highest headline figure, because of difficulties in comparing like with like.
The Prudential's initial offer was valued at pounds 2.2bn but this included a pounds 1.5bn loan to the ScotAm life fund. That would help it invest more profitably in the long run but would not have the same appeal to policyholders as a large cash bonus or allocation of shares.
The final bids, made under conditions of secrecy, may however have narrowed these differences.
AMP admits to being the outsider because it is Australian-based and still a mutual insurer, although it is the most determined to expand its European operations through a takeover and is unlikely to be the lowest bidder. It is, however, making contingency plans to launch a bid elsewhere if it fails to win ScotAm.
Abbey National was the first to show its hand and already has a strong Scottish presence through the ownership of the Scottish Mutual.
Last the week the City gave Abbey the dubious privilege of installing it as favourite to win through an overpriced offer and responded by selling Abbey National shares. They were down 8.8 per cent, and the Prudential 6.4 per cent, but over the weekend the Prudential was installed as slight favourite.
Shares in the Pru fell a further 3.5 per cent yesterday, partly on fears that insurers would be saddled with the cost of American tobacco companies compensating smokers.