Several entrants at this year's Cresta Awards asked us to critique their case videos. And it made us think about the role of these films at today's creative festivals. Can a great video lift the results of average work? Or a dull one reduce even great work's impact on a jury?

Arguably, case videos have become almost as much a skill as the work itself. And, as with any creative work, there's some that seem a little formulaic and others that shine through as being inventive and innovative. Great ads for great ads, you might say. We've picked five of our favourites this year. All of which helped their entry win either a Grand Prix ( BETC São Paulo’s Usain Bolt biography for Puma, above) or Gold Award. So check out these case videos below, and see what you think.