Miss Fisher and the Crypt of Tears, for example, comes five years after Miss Fisher's Murder Mysteries finished but obviously the makers thought it would be well enough remembered by its fan base to take the punt - a considerable amount of money was raised through a crowdfunding campaign. It's clearly a direct follow-up to the series aimed mostly at fans. At least it's a completely new movie.

Other Australian TV shows had movie spin-offs. Skippy the Bush Kangaroo had Skippy and the Intruders and Number 96 was adapted into a racier movie of the same title, both released during their respective show's original run.

In the US, Batman had a new movie released after its first season in 1966 and The Lone Ranger had one movie come out during its run and one soon after it ended. The Legend of the Lone Ranger (1981) became "legendary" for the badness of its lead, Klinton Spilsbury, whose voice was dubbed and who never made another movie.

Making movies during a TV show's run has obvious advantage, like the cast still being together and audience familiarity at its peak. Sometimes producers take the laziest option, editing episodes of TV shows together and releasing them as "new" movies.

Disney had considerable success doing this with Davy Crockett in the 1950s. The Crockett craze with its raccoon caps was so great that people paid to watch what they had already seen for free. The 1960s spy series The Man from UNCLE had some of its double episodes released in cinemas but added new, sometimes more adult, footage making for a slightly different experience.

Speaking of The Man from UNCLE, it was one of many TV series adapted to the movies long after the original run. This trend seemed to become popular in the 1980s. Another 1960s spy show, Get Smart had a belated cinema spin-off with original lead Don Adams, The Nude Bomb (1980), a cheap and unfunny movie lacking the original's appeal, and a dull remake with Steve Carrell.

But some shows, like The Fugitive and The Untouchables have resulted good movies in their own right, whether you knew the original series or not. Ditto the seemingly endless (if uneven) stream of Star Trek movies, the appeal of which has moved beyond the hard-core fans of the original show.

A lot of shows made into movies have been somewhat spoofy, like The Brady Bunch Movie (1995), which transplanted the innocent Bradys into the more cynical 1990s and also traded on references to and legends about the original. 21 Jump Street also worked. Others like Starsky and Hutch and The Dukes of Hazzard came and went.

Some redos seem curious: would a younger audience know or care about the 1960s Gothic soap opera Dark Shadows, and would older people who might remember it care enough to see it redone? Apparently enough did - or were fans of Johnny Depp and Tim Burton - for it to do modestly well.

It's the kind of thing that ensures TV shows will continue to be mined until My Mother the Car becomes a movie.