Imogen Heap's Twitter fans help make her music
Singer Imogen Heap explains the role of Twitter - she has 1.5m followers - with input from her fans into her music and how she is looking forward to video tweets.
The panel discuss the impact of the social networking site which has just celebrated its fifth birthday, but Michael Portillo does not tweet - preferring the telephone to communicate with "both my fans" - and Hazel Blears claims she is "not allowed" to join in.