This is the big one. Not just the finale of The Secret Service but the end of an amazing decade for the crew of Century 21 Films in Slough perfecting the techniques of Supermarionation filmmaking. Once this episode was in the can, the puppet stages on Stirling Road closed for good on January 24th 1969 … until Thunderbirds returned to the trading estate in 2015 for the production of three episodes to celebrate its 50th anniversary, but that’s another story.
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