Supplementary data associated with a broadcast transmission (5, 26) is made available to the viewer by identifying the content currently being received at a user terminal (2). The user generates a request for data which includes the identity of the broadcast content. This request is transmitted from the user terminal (2) to a content provision platform (4). The content provision platform retrieves supplementary data associated with the identified broadcast content and delivers the supplementary data to a predetermined return address (9).