the synchronisation request the as 400 sends a buffer media command to each ue alternatively in embodiments which do not involve the as 400 the buffer media command may be sent by the ue 100 prior to sending the play media command each of the ues then buffers the streamed media from the iptv service and once enough of the media has been buffered sends a buffering complete notification to the as 400 or the ue 100 which then sends a play media command comprising a timestamp as before this avoids the potential situation where a user with a slow internet connection may miss a portion of the start of the media stream as their ue is unable to buffer enough media to begin playout when the timestamp occurs fig7 shown a signalling diagram for a method of adding a participant to an ongoing social tv session ues 100 200 and 300 are involved in an ongoing conference voice call and tv sharing session with the current position in the media stream being synchronised by the as 400 or the ue 100 in embodiments not involving the as the ue 700 is added to the conference the as 400 or ue 100 sends a play media command to the ue 700 the play media command comprising a timestamp and an offset the timestamp and offset are chosen such that the synchronised media stream would reach or has reached the offset at the time indicated by the timestamp e g a timestamp of 18 44 42 12 and offset of 160 62s would indicate that each of the ues 100 200 and 300 was or would be expected to be 160 62s from the start of the media stream at 18 44.