In the wake of the storm over “trading huddles”, there are new mutterings of investment bank tip-offs to preferred research clients.

Consider Baidu, the $14bn Chinese search specialist listed on Nasdaq. The stock had an uneventful summer, beginning July at $301 and ending August at $330. At about 10am on Friday September 4, it suddenly surged against a flattish benchmark. By 1pm, the stock was up 5 per cent. Over the next three trading days, it continued to rise. On September 11, Goldman Sachs upgraded earnings estimates, with a higher target price – $475 – than any of the 23 brokers on the street. On Wednesday, Baidu broke through $400.