 Filming of Series One was completed in December 1965 . A second series was also commissioned late that year and entered production in March 1966 . <unk> became a full @-@ time member of the writing staff and took over the role of script editor from the outgoing Pattillo . The main puppet cast and vehicles were rebuilt ; in addition , the art department expanded some of the standing sets , including the Tracy Villa lounge and the Thunderbird 5 control room . To accommodate the simultaneous filming of the TV series and Thunderbirds Are Go , APF purchased two more buildings on the <unk> Trading Estate and converted them into new stages . As crew and studio space were divided between the two productions , filming of the TV series progressed at half the previous speed , as APF 's B crew produced one episode per month . Filming on Thunderbirds Are Go was completed by June , allowing A crew to resume work on the series to shoot what would prove to be its penultimate episode , " <unk> " . 
