KT Tunstall and U.K. indie-rock acts the Charlatans and Starsailor are to play Hard Rock Cafes in the U.K. as a warm-up for the Hard Rock Calling festival in London's Hyde Park June 28 and 29.

The Charlatans will play the first show of the Road to Hard Rock Calling series at Hard Rock Cafe London on April 24. KT Tunstall will appear at Hard Rock Cafe Edinburgh on June 3 and Starsailor will play Hard Rock Cafe Manchester on June 19.

They will also appear on the bill for Hard Rock Calling, alongside Eric Clapton, the Police, Sheryl Crow and John Mayer. The Live Nation-produced festival is part of Hard Rock's third annual Ambassadors of Rock Tour, a global concert series which benefits charities worldwide.

"Hard Rock's Ambassadors of Rock concert series continues to be one of the world's premier music events," says Sean Dee, VP and CMO, Hard Rock International in a statement.

Tickets for the Hard Rock Café shows are being given away on Virgin Radio and the station's Web Site, www.virginradio.co.uk.