SOLUTION:We made the most of the fact that the Metro line (L10) which goes to the zoo and the fun fair in the Casa de Campo Park is underground until it breaks out of the tunnel just as it reaches the Casa de Campo to demonstrate how quickly the sun can burn your skin. We placed several apparently conventional portraits in the Metro trains, on which, while the train was in the tunnel (against a dark background) users could read a solar protection message. But when the train came out into the daylight (against a bright background) the faces in the portraits appeared completely burnt by the sun, with the message: “The sun burns more quickly than you think.”

RESULTS:The 9,517,717 people who use the L-10 Metro line in Madrid every month claimed this “magical” demonstration served to open their eyes and help them realise the need to protect themselves from the sun at all times. Indeed, 97% of the people we interviewed just after seeing the action said so.*