As audit fees for the FTSE 100 head towards £600m a year, it is the stark reality that there are only four players in town as far as public interest entities are concerned. The Big Four simply swap between each other, pitching for the blue chip audit business which they alone are equipped to handle.

Without doubt audit firms outside the magic circle would like to secure a seat at the main audit table, but ultimately they do not have the depth or international reach to offer the scale of services, not to mention specialist audit staff in-house, to win the audit business. At the same time, the level of risk associated with a major FTSE 100 audit can be deterrent enough for those outside the Big Four.