It’s a great premise for a comedy, picking up after the point most alien invasion movies end to imagine just how the extraterrestrials might rule their new domain.

And they turn out to be just as useless at governance as humans, at least in the minds of We Are Not Alone writers Ben Willbond and Laurence Rickard – both of Ghosts fame – who have created this thoroughly engaging feature-length special.

Placed in charged of Territory 78 – as the UK is now known, after nations got ranked purely in terms of size – is the inept politician Trater, played by Vicki Pepperdine, whose need to be liked means she’s always trying to ingratiate with the locals. However the highly-strung soldier Gordan would prefer a more militaristic approach. It says something about the likability of your cast when Mike Wozniak plays the bad guy.

Aiding them run the country from the new capital of Clitheroe – the logical choice since it’s the geographical centre of the land mass – is hapless underling Greggs (Joe Thomas) and a human reluctantly recruited as the liaison with the native population, Stewart. In a cast of well-known comedy faces, relative unknown Declan Baxter does a fine job at playing the underachieving Everyman not wanted to get involved with this ‘new normal’ but ultimately having to pick sides between his alien paymasters and the human resistance movement, masterminded by former Defence Minister (Amanda Abbington). What side he chooses may eventually be down to pub owner Elodie (Georgia May Foote), whom he desperately wants to impress.

It’s easy to read We Are Not Alone as a satire on the British Empire, given its based on an invading force with an apparently gentle, ‘jolly good chap’ front backed with unbeatable military might, but any such points are lightly made.

Jokes comes from the day-to-day decisions the alien Gu’uns have to make in controlling and working with the humans, as well as their ultimate outsiders’ viewpoint highlighting the absurdity of our behaviour. A nice running gag is that they believe the hands up of surrender to be an Earth greeting. Though not in his league, there’s a touch of the Douglas Adams about the way quotidian concerns undermine the usually epic scope of sci-fi.

Outright jokes take second billing to the story, however, so it’s more smileworthy than laugh-out-loud. But viewers will be drawn to the story and the diverse array of characters, with strong comedy cameos across the board, including Evelyn Mok as a taciturn IT geek, Rob Delaney as the ruler of what was America and Miles Jupp as the deposed Prime Minister.

Rarely has the subjugation of the human race been depicted so charmingly.

• We Are Not Alone is on Dave at 9pm tonight. Read an interview with Ben Willbond and Laurence Rickard here.