For Doctor Who fans, the trips in time and space that the TARDIS didn't take are every bit as fascinating as those it did – in some cases, more so.
One of the BBC sci-fi show's most famous abandoned stories is 'Lungbarrow' – originally pitched for the Sylvester McCoy era on TV, writer Marc Platt's script would have explored the Doctor's ancestral home on Gallifrey and revealed secrets of the Time Lord's past.
Though the story was never made, aspects were reused in Platt's season 26 serial 'Ghost Light' in 1989 – Platt also later wrote a version of 'Lungbarrow' as a novel, which was published in 1997.
Doctor Who: Season 26 – The Collection is coming to Blu-ray next month, with the show's late '80s script editor Andrew Cartmel discussing the reasons behind scrapping the TV version of 'Lungbarrow' at a recent BFI screening to promote the boxset.
"That was too internal a script to really work as a drama," Cartmel explained.
"It was a brilliant, kind of gothic notion, but I think it was ideally suited to the novel that he (Platt) turned it into, into a sort of (Gormenghast author) Mervyn Peake prose thing."
He continued: "In a way, it was a very useful exercise doing 'Lungbarrow' with Marc, because it was a fantastic playground for ideas, which later found their way into 'Ghost Light'.
"But I think as a piece of mainstream television drama, it just couldn't really have happened, because it was too inward, too internal, too inherently undramatic."
'Ghost Light' along with the stories 'Battlefield', 'The Curse of Fenric' and 'Survival' ended up making up Doctor Who's 26th season, the final run of episodes from the show's classic era.
Doctor Who: Season 26 – The Collection is out on Blu-ray on 23rd December and is available to pre-order now