Ward said she is leaving to spend more time with her family. She is currently negotiating her departure date, but is likely to be with the agency until the end of the year as she hands over major accounts such as Cadbury's, Coca-Cola, Unilever and Mastercard.
Ward, a consumer PR expert with 20 years' experience, has been with WS for the past five years, having joined from Porter Novelli, where she was business development director. She currently sits on the European board of WS and reports to Tim Sutton, chairman, Europe.
Former Sun editor Yelland is quitting as senior vice-chairman of Weber Shandwick after two years to become a partner at City PR rival Brunswick.
Yelland, who resigned from the Interpublic-owned agency yesterday, is on a three-month notice period, making him free to join Brunswick in October.
He also worked on the agency's accounts with Coca-Cola and Multiplex, the Australian developer at the centre of the Wembley Stadium fiasco.
Yelland is understood to have been attracted by the allure of working on major mergers and acquisitions at Brunswick, which represents around a third of FTSE-100 companies. It recently handled Greg Dyke's bid for ITV.
He has been good friends with Brunswick founder and senior journalist Alan Parker since his days on The Sun's City desk in the late 1980s.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the Forum.