UK insurer Prudential’s bid for the Asian assets of AIG may have ultimately come to nothing, but in one area it helped seal the importance of what is becoming a significant trend in investment banking – the use of an adviser to offer a fairness opinion.

Although the timing was unusual - fairness opinions are usually sought before a deal is recommended, not some weeks after as in this case - and although it was the potential acquirer, not the target, the deal is the latest and arguably most high-profile example of a second opinion on a takeover.