Actors Forest Whitaker, Hugh Grant and Keira Knightley have signed up to perform on a special charity edition of hit US TV talent show, American Idol. They will be joined by Daniel Radcliffe, Helena Bonham Carter and Desperate Housewives star Terri Hatcher on American Idol Gives Back, a one-off programme to raise money for children in Africa and those whose lives were severely affected by 2005's Hurricane Katrina. Some celebrities will take to the stage alongside pop singers such as Gwen Stefani and Pink, while others will use their popularity to encourage viewers to donate funds to the charities. A source says, "It's great to have such a strong array of A-list stars. We are getting a chance to expose a young audience to global issues." The show will be broadcast live later this week (begs23Apr07).