According to the documentary accompanying the Network DVD release, the concept for this show originally envisioned it as a programme aimed at youngsters in the mold of other children orientated sci-fi such as The Tomorrow People or Doctor Who. However the documentary goes on to state that this idea soon dissipated when the two stars (McCallum and Lumley) were signed, the production costs subsequently spiralled and made it impractical to keep this as part of childrens TV programming. The programme was then written for an older (i.e. teenage) audience in mind and moved up the schedules from a childrens tv slot to an early evening slot (most ITV networks screened it around 7pm). Despite the big name casting and sci-fi elements the show was not a massive hit not because of perceived lack of quality but because the haphazard way it was produced with the stars availability together for filming being restricted due to other commitments. This meant that the show could never really get a strong foothold in tv programming due to the irregular way the stories were becoming available for transmission. Without a regular production schedule the shows ended up showing at different times and dates all across the ITV network and as such production eventually fizzled out with some ITV networks not showing the final stories until 2 years after they had been filmed.
The original idea was for Sapphire's powers to be signified by a throbbing blue vein on her forehead, this was ultimately replaced with her eyes turning a vivid shade of blue.
The name of the serials that appear here and appear on some DVD releases never show on screen at any time. Creator Peter Hammond has also confirmed that the names were not part of production documents and the episodes were only given numbers. The names also don't appear on VHS releases of the series. It is believed that the serial names were given by fanzine authors to make discussion of series easier, but this has not been able to be confirmed.
The reason behind the series' cancellation was both actors, Joanna Lumley and David McCallum were in such high demand and busy with other projects, its renewal for another season never happened.
The cliffhanger in (what became) the final season was to be resolved in a following season - however at the end of 1981 the production company ATV lost its franchise to broadcast and production was closed down. Its successor Central TV was reluctant to carry on screening the yet to be transmitted episodes (being more interested in game shows/variety) but viewer pressure saw them finally get aired in 1982.