tim bellTim Bell, the UK PR mogul behind global PR institution Bell Pottinger, has left the firm to start a new PR consulting venture next year.

Seventy-four-year-old Bell, who parlayed his stint as Prime Minister Margaret Thatcher's spokesman into the successful agency, will open Sans Frontieres.

Bell Pottinger said in a statement that Bell wanted to "step back" from day-to-day agency business but still counsel clients. CEO James Henderson called Bell the "founder and driver of this business since he started it in 1987."

Henderson said BP will "find ways of mutually working together with [Bell] in his new business where there are clients that need a combined expertise." Bell retains a minority stake in BP.

Mark Smith takes over the chairman role at BP.

Bell in 2012 helped orchestrate the $32M buyout of BP from Chime Communications.