Downton Abbey one of the latest movie adaptations of TV shows

This goes back at least as far as the 1950s when The Quatermass Xperiment was made, based on the BBC TV serial from a couple of years earlier. Other British big-screen spin-offs include Porridge in 1979 and Dad's Army in 1971 and 2016.

Sometimes the movies literally are TV shows: they can be big-screen versions, often re-edited, of pilot episodes like the original Battlestar Galactica (1978). Other times they're re-edited compilations of series episodes, like Davy Crockett, King of the Wild Frontier (assembled from three episodes of the 1950s Disney TV series).

And the same thing has happened with some of the network mini-series popular in the 1970s and '80s: for example, Salem's Lot (1979) was converted into a much shorter movie including some alternative, more violent, takes.

Occasionally the movie adaptations are concurrent with the series to capitalise on the latter's popularity: Batman (1966) brings together the villains Penguin, Joker, Riddler and Catwoman in what plays like an elongated episode of the show. The X-Files had two big-screen outings: one in 1998 while the original show was still in production, another a decade later after it had been revived.

Since the 1980s there have been many small-to-big-screen adaptations, including Twilight Zone: the Movie (1985), Dragnet (1987), Get Smart (belatedly spun off as The Nude Bomb in 1980 with original Smart, Don Adams: in 2008 came a feature film with the original title).

Saturday Night Live inspired, if that's the word, a lot of movies based on recurring characters, but often what works in a skit doesn't bear expansion into a feature film (e.g. A Night at the Roxbury). The Blues Brothers' deadpan was enlivened on the big screen by car crashes and musical guest stars and the Wayne's World movies were amusing.

There are many ways to exploit the familiarity of a title. Some adaptations are direct sequels like Downton, others are revamps of the same story (The Fugitive), and still others are spoofs (21 Jump Street).

Animated series, as we've seen, are not immune either. Besides inspiring a live-action version decades later, The Flintstones, at the end of its run, had the 1966 Fred-as-secret-agent feature The Man Called Flintstone. The title seems like a nod to titles from the spy craze of the 1960s like The Man From UNCLE: the latter had episodes packaged together as movies and also, a bit perplexingly, received a 2015 movie rejig (was it supposed to appeal to baby boomers?)

On the horizon is an animated version of The Addams Family (1960s TV series became 1970s cartoon became 1990s movies, to name the previous major manifestations). Also reported to be coming are films based on Breaking Bad, V, and more.

It looks like TV adaptations, good and bad, will be with us as long as movies and TV themselves.