Outdoor: Special report

A single, 30-sheet outdoor ad, displaying just two words, and which appeared in one location only, caught the eye and imagination of Cannes jurors this year. So powerful was the idea that it almost stole the Media Grand Prix.

The ad was for McDonald's, created by Leo Burnett, Chicago. It eventually lost out to Forsman & Bodenfors' web-based campaign for AMF Pensions, in which young people could post photos of themselves and have them digitally "aged".

McDonald's and its agency worked with Greg Pierceall, a professor of horticulture from the University of Illinois, to develop a method of growing lettuces from a vertical plot - this was the "poster" site. Seeds were planted in what looked like red clay soil and over the course of three weeks or so, grew to form the words "fresh salads". The iconic M-shaped "arches" logo was the only other adornment.

The ad didn't take the top media prize, partly because it was a one-off, and the innovative and effective Swedish campaign was a worthy winner. But its high profile demonstrates the impact that one outdoor ad can make.

That HBO's "voyeur" campaign cut a swashbuckling swathe through many of the Cannes awards this year also says much about the resilience of outdoor as a medium. The projection of film on to the side of a New York building, which appeared to show what its occupants were doing and created a storyline between them, was an eyeball-popping demonstration of the power of large-scale, mass communication in an era of ever-tighter narrow-casting.