As ebullient executives toasted Bank of China's initial public offering last week and breathless investors chased its shares higher, one group sat purring contentedly in the background.

Gratified by their lucrative role in the $9.7bn (£5.2bn) flotation were auditors from PwC, who had knocked the bank's books into shape. They had surpassed rivals at KPMG, which audited China Construction Bank for its $9.2bn IPO last October. But PwC itself is likely to be trumped by Ernst & Young if, as expected, Industrial and Commercial Bank of China launches a $10bn-$15bn offering in September.