When a haul of forgotten reel to reel audio tapes from AP Films in the 1960s landed on our doorstep, the prospect of what could be on them filled us with curiosity. Could they represent a treasure-trove of lost sound effects or had they all been wiped in favour of 1970s pop hits? In this Thunderbirds Unseen Update we detail the process of uncovering their contents – a process that involves careful playback of 60 year old quarter inch tapes, researching the methods used to record and re-record onto them, and some fascinating recoveries. Join us in Thunderbirds Unseen as we go behind the scenes of the transferring and cataloging of a treasure trove of previously lost television moments.