The Coca-Cola Challenge.

Coke's ad strategy has fluctuated between global and local for years. Jane Bainbridge asks if the new call for an iconic ad message will bring some consistency to the brand.

In ten years, Coca-Cola has gone from 'always' to 'enjoy' to 'real' with a bit of 'life tastes good' thrown in for extra spice. For the world's most valuable brand, this hardly constitutes a consistent advertising message.

Add its ever-changing global-versus-local philosophy into the mix and you have something of a rollercoaster strategy.

Last month, the 'pendulum client', as one ex-agency source dubbed Coke, revealed that, once again, it was looking for a global advertising message in a bid to regain something of the iconic nature of its classic campaigns such as 'hilltop'.

The problem for Coke is that 'hilltop' was 30 years ago. In the past decade, the brand has conspicuously lacked a global campaign of anything like comparable strength.

But it's not for want of trying. Ten years ago, its then-chief marketing officer, Sergio Zyman, shook up Coke's advertising by turning his back on global agency networks and hiring the likes of Creative Artists Agency (CAA), a Hollywood talent business. His philosophy was that he wanted the most talented people, no matter where they were from.

But despite breaking out of the confines of the agency networks, the focus remained global. 'The rule was all creative ads came out of Atlanta and the exception was promotional work,' one source says.

CAA's polar bears work under the 'always' banner proved to be one of the …