As part of the changes, Chris Hayward, the long-time UK trading director of ZenithOptimedia, will now report to Locke, as well as to the ZenithOptimedia UK management.
VivaKi launched its UK trading arm in September 2008. Although Locke was originally the lead on the operation, Hayward and he have worked together as joint trading directors of VivaKi.
While Locke will continue to have responsibility for some SMG clients, the move means John Baylon, who was promoted to head of trading in September 2013 following the departure of John Davidson, will take on an enlarged role.
Locke has been with the group for 24 years through its various iterations. He joined the media department of DMB&B, which became The Media Centre and then MediaVest in 1999. MediaVest merged with Starcom in 2001 and Publicis Groupe then bought the group in 2003.
Adrian Sayliss, the UK chairman of VivaKi, said: "Since the start of VivaKi, Chris and Chris have worked behind the scenes together with the media owners. Chris [Locke] will now take more of an overt leadership position in the market place for us.
"[The change is] in response to the complexity of the market place. It's more of an evolution than a great change. We need one voice when having conversations with media owners.
"We're not just doing ITV deals – they have digital, partnerships and that's the case for all media owners. We need to work out how we best converge all our assets and bring best practice for our clients."
Tim Neligan, the former chief operating officer of ZenithOptimedia, was promoted to commercial director of VivaKi in November.Follow @MaisieMcCabe