Mike Love is set to join B-M next week, following the departure of Gavin Grant last year to become chief executive of the RSPCA.
Until March, Love led strategic comms for G4S' cash transportation arm, G4S Cash Solutions. He previously held pan-European roles at McDonald's and Microsoft.
Love also had a career in political campaign management, including five years as party agent to then prime minister Margaret Thatcher.
As chairman, he will work across B-M practices on pitches and new business, as well as providing counsel to clients. Love will report to chief executive Matt Carter.
The move is Love's first agency-side role. He told PRWeek he knew the agency well, having worked with B-M in several of his roles.
The appointment follows B-M's creation of a worldwide leadership team to oversee global business.
Chief executive officer for EMEA, Jeremy Galbraith, takes on the additional role of worldwide vice-chair for strategy.