Trading Places (9 Apr): This week's people moves in advertising, marketing and media

Digital

Steak co-founder Julian Walker has left after five years at the helm of the digital agency to pursue new interests. Walker, who co-founded the agency in 2005 with chief executive Oliver Bishop and head of paid search Duncan Parry, will not be replaced. (Campaign)

Michael Steckler, AOL UK's former managing director, has joined the personalised retargeting business Criteo. Steckler will join the business on 4 May as its first managing director, nearly three months after leaving technology giant AOL. (Media Week)

Marketing

Muller Dairy has appointed internal candidate Jonathan Dee as its interim marketing director in replacement of Chris McDonough. McDonough joined Molson Coors, the beer company, in February this year. (Marketing)

MasterCard Worldwide has promoted Alfredo Gangotena to the position of chief marketing officer, with immediate effect. He replaces Lawrence Flanagan, who is to retire after 10 years in the role. (Marketing)

Media

Outdoor media owner Admedia has appointed four new sales people, Peter White, Neil Boyle, Matt Gardiner and Cedric Rouse, who will work across client, agency and specialist sales. (Media Week)

APA, the customer magazine association, has elected Ellen Brush, the managing director of Axon Publishing, as its new chairwoman. Brush replaces Martin MacConnol, chief executive of Wardour, who had been in the position since 2008. (Media Week)

Charly Classen, senior director of business development for EMEA at ESPN, has taken on the additional role of commercial director for the UK as the sports broadcaster ramps up its London based operations. Classen reports to Lynne Frank, ESPN's managing director of Europe, Middle East and Africa. (Media Week)