British singer Jamie Cullum is set to hit new heights at an upcoming gig - he is planning to perform on the roof of a London building for charity. The jazz star will head to the top of the headquarters of the Shelter organisation, which helps the homeless, for a show on Tuesday (21May13). Fans can watch the concert online and make song requests via Twitter.com, and the company's chief executive Campbell Robb says, "We're so excited Jamie is coming to Shelter. This is the first time we've ever had someone perform live at our offices, let alone on our roof... It's great to have Jamie's support."