By Matt Elias

“Sensitive songs out! Thumping songs in!” That’s KT Tunstall’s formula for making the best festival set list — a secret she shared with us recently at the two-day Hard Rock Calling concert in London's Hyde Park.

There is an exception to the rule, though, especially if you’re going to treat festival-goers to a brand-new song. “Tonight I’d actually like to play a new song of mine which is a total spooky little picker,” KT said. The song is called “The Hidden Heart,” and she’s only played it live three or four times. Here's the story behind the new number, in KT's own words:

By Matt Elias

Sunday night marked a momentous day in the U.K. as the Police played their last-ever show there — and MTV News was there to cover it all. London’s Hyde Park was the location, and fans packed shoulder-to-shoulder to catch their last glimpse of the trio, who were Sunday’s headliners at the Hard Rock Calling music festival.

Eric Clapton headlined Saturday night’s show, with Sheryl Crow, John Mayer, KT Tunstall, Jason Mraz and Starsailor rounding out the festival’s bill. Fans were treated to gorgeous, rain-free weather on both days, and were treated to a special Saturday night performance when Clapton encored with special guests Mayer and Crow on “Crossroads.”

Of course all the talk backstage was about the Police playing their last U.K. show and about Eric Clapton, since both have had a strong influence on the bands that took the stage before them. Check out photos from the show, and watch our full wrap-up below:

You can also check out my show reviews from both days of the festival over at You R Here.