The unforgettable sight of Thunderbird 1 blasting into action from beneath an island swimming pool in the South Pacific has remained in the minds of viewers for six decades. Now, with previously unseen footage, behind the scenes stills material, and archive research – Thunderbirds Unseen reveals the making of this iconic sequence. In this extra instalment of our behind the scenes investigation of the creation of Gerry and Sylvia Anderson's classic television series Thunderbirds, we take an in-depth look at the Thunderbird 1 launch sequence. With the help of newly unearthed 35mm film and studio documentation, this series challenges some of the "established" facts of the series' early days and uncover footage unseen for sixty years.