The Grand Prix went to Droga5 for its "decode" campaign for Microsoft Bing.
The work, which showcased the search engine's capabilities by seeding pages of Jay-Z's autobiography in different locations around the world, has now won Lions in three categories, and is also hotly-tipped to triumph in the Titanium awards later this week.
Overall eight UK agencies won Outdoor Lions, double the number which triumphed last year.
Abbott Mead Vickers BBDO won the only UK Silver for its "road safety" campaign for Tower Hamlets, which warned drivers about the perils of texting while at the wheel.
Five UK agencies won Bronze, including JWT London, which followed up last year's success in the same category by winning with Listerine.
M&C Saatchi won Bronze for its work with Elephant magazine. The ad, which featured the letters Eleph and a picture of an ant, was Graham Fink's last campaign with the agency before he joined Ogilvy China.
The final UK Bronze awards went to Publicis London, OgilvyOne and Mindshare. Publicis was awarded for its "12 second strip" campaign, which challenged members of the public to change from their winter clothes to summer wear in 12 seconds – the amount of time it takes to fold up the roof of the Renault Wind Roadster.
OgilvyOne's Bronze came for its "Lotus T5" execution for IBM, while Mindshare was recognised for its "angel ambush" Lynx ad.