The closest challenger to the Big Four this decade, Grant Thornton is a firm that has always prided itself on being dynamic and willing to do things differently.

In 2007 the firm pushed ever closer to the psychological £500m revenue barrier with the bold acquisition of struggling rival Robson Rhodes, and has used the deal as a symbol of its intention to shake-up the accounting establishment and provide a genuine challenge to the Big Four.

The firm still has some way to go yet. Revenues for 2007, including the Robson Rhodes deal, are still only at £387m and although it is ranked among the leading auditors and advisers on London's AIM market, it has still struggled to make an impact in the FTSE 350 space.

This is something the firm has openly said it is determined to change. Grant Thornton is blessed with many of the profession's brightest personalities and pushes its image as the friendly face of accountancy.