Like a philandering husband coming home to his long-suffering wife, Coca-Cola has returned to Interpublic to face what may be an uncomfortable old age.
The world's most famous brand is not quite the virile young buck it once was. Its youthful good looks have faded as worldwide sales have flagged and investors have grown less ardent about it. Where once it could boast a clearly defined personality, it now faces an identity problem, with consumers unsure what Coke is anymore.
After a decade spent pursuing any number of mistresses, IPG now provides a high comfort factor for Coke. The relationship between the two stretches back to the 50s and IPG deserves having a glass of fizz raised to it for hanging on in when links between network and client appeared terminal.
Indeed, there were many who believed that Coke's decision in the early 90s to trawl more widely for creative work beyond the IPG-owned McCann-Erickson marked a fundamental shift in the balance of power. If the likes of Coke were going to cherry-pick their creative merely to have their networks implement it, how long, many argued, before other global clients followed suit?
So what's to be deduced from the reunion under which IPG has been charged with defining and safeguarding the 'brand essence' of Coke in its key North American market as well as 198 other countries?
Firstly, that Coke recognises the need not only for creative but cohesive advertising. The Coke brand accounts for 60 per cent of the company's global volume and, while its distribution network is awesome, the key to its continued growth will be getting the message right. This is particularly true at a time when Coke faces ever-intensifying competition from own-label colas, new-age drinks, mineral water varieties and, of course, Pepsi.
Secondly, the switch says much about the way network leviathans such as McCann have transformed themselves over the past decade. McCann lost Coke because it refused to think the unthinkable - that its flagship client would ever seek satisfaction elsewhere.
In short, McCann lost out because it failed to exploit its huge storehouse of knowledge about the Coke brand in the service of its client. Now it has the resource and the will to do so and John Dooner, IPG's president, talks of bringing Coke a comprehensive range of solutions, from advertising to in-store and digital marketing.
If Coke's homecoming proves anything, it is that agencies have no divine right to be brand guardians. They must constantly prove to be worthy of the accolade.