The competition, Copywriting Goes Underground, challenged creatives to produce a long-copy 48-sheet poster for a live client containing no fewer than 50 words and aimed at London Underground passengers.
Tony Curran and Phil Webb came up with the winning execution, which showed famous images within picture frames. The copy reads: "Classic images.
Unfortunately, nothing can truly replicate the richness of detail and intensity of colour you get with Epson photoprinters, so we had to resort to words instead."
The poster, chosen from more than 150 entries, will now run on sites at 25 major London Underground stations for two weeks during this summer.
A poster for Budweiser, by Ted Heath and Paul Angus from Rainey Kelly Campbell Roalfe/Y&R, was also highly praised by the judges.
Mike Baker, Viacom Outdoor's European marketing director, who was one of the judges, said: "It's great to see that the art of the copywriter is still alive and kicking."