Produced by Sydney Newman, who went on to be a key figure in the creation of Doctor Who, and co-written by Malcolm Hulke (who would later create the Silurians and the Sea Devils), Pathfinders is a significant precursor of the series.
Itself a sequel to 1960's Target Luna, it sees a core gang of travellers travelling to the Moon, Mars and Venus over the course of three series (first aired from 1960-1961), encountering such things as the crystallised remains of a 400 million-year-old man, dinosaurs, and Venusian cave people.
Network have just reissued the trilogy on DVD. Extras include PDFs of the scripts for Target Luna (which no longer exists in the archives), and a detailed booklet by TV historian Andrew Pixley. We have three box sets to give away. To put your name in the hat for the chance to win one, simply answer the question below.