Knox, who retired as FD chairman in 2000 only to return after the firm's second management buyout in 2003, told PRWeek he had decided to make way for 'a new pair of hands'.
UBS Investment Bank vice-chairman Oliver Pawle, who joined FD's advisory board last April (PRWeek, 9 April 2004), has replaced Knox.
Knox, who remains a non-executive director at FD, said he would keep his equity and help with Advent International's sale of its 55 per cent stake in the company, which could happen in the next two to three years.
'We need quite a lot of time before we can demonstrate to the market that the acquisitions we have made since the MBO have worked,' he said.
Knox revealed that he wanted to take on similar advisory roles on the boards of other private equity backed business but at 60 did not plan to take on a full-time position.
He has worked in PR since 1967 and founded his first IR and financial communications shop, Financial Strategy, in 1978.
Knox set up Financial Dynamics in 1986 but retired in 2000 after the firm's then chief executive, Nick Miles, led the first MBO of the company from GGT.
Knox returned after a second MBO from Cordiant Communications, led by current chief executive Charles Watson and backed by Advent, in 2003.