Thunderbirds Are Go in this behind the scenes look at the production of "City of Fire", a fabulously flame-grilled episode of Gerry and Sylvia Anderson's Thunderbirds remembered by many for its visual scale and action set-pieces. In this deep-dive making of, we use original scripts, newly-unearthed film material, and other unseen production paperwork to shed new light on the episode. Originally planned as a 25 minute adventure, "City of Fire" was extended once the order was given for Thunderbirds to rocket into the fifty minute format.