Coca-Cola's latest outdoor innovation is a light-sensitive poster devised by Des O'Meara & Partners. Seen during daylight hours, it depicts an image of children sitting in front of a Christmas tree. Once darkness falls, a light sensor pushes through the second image - of Santa in the same room.

The poster is part of the brand's traditional "holidays are coming" campaign which is running on TV, radio and cinema.

Last month, Coca-Cola also tried out an outdoor advertising idea but with less success. The company owns a permanent poster site at the Point Theatre and its technically ambitious poster featured a giant cut-out of the Coca-Cola bear who is supposed to cry copious amounts of real watery tears.

It worked on the all-important night of the MTV awards but thereafter the tears dried up, due to a plumbing problem.