“Last time on 21 Jump Street . . . " booms the voiceover before the montage. Prepare for some lessons in the grammar of 1980s TV.

Many heads were scratched when 21 Jump Street hit the multiplexes in 2012. Why would anyone want to make a movie based on an old common-garden cop show, remembered only, if at all, as the vehicle that launched Johnny Depp? Was the entire barmy idea conceived around a Depp cameo?

Then, curiouser and curiouser: the newer, hipper, ingeniously self-deprecating 21 Jump Street turned out to be pretty, damned funny. Might this similarly unlikely sequel repeat the trick? Apparently so.

Knowing sequelitis has been improving unexpected instalments since Shakespeare's Henry IV, Part 2, and in keeping with this long tradition, 22 Jump Street makes merry with the meta-jokes. As mismatched officers Schmidt (Jonah Hill) and Jenko (Channing Tatum) return to the undercover beat, their perennially miffed captain (Ice Cube) outlines their policing and franchise duties: the pair will do exactly what they did last time, but with a bigger budget. "I got a big ass raise to babysit you two fuckers again," observes Mr Cube, sagely.

And so 22 Jump Street resets to zero in inverted commas. Except that this time, they'll be going undercover on a college campus, not a high school. "I'm the first member of my family to pretend to go to college," says Jenko, tearfully. And so on.

There follows some shenanigans with a drug operation, various keg parties and a detour to Puerto Rico for spring break. But, mostly the film concerns itself with the on-again, off-again bromance between the neurotic Schmidt and the meat-headed Jenko. That’s as it should be: Hill’s uptight comic schtick finds a perfect foil in Tatum’s perfectly pitched slow blinks.

The pairing, like the movie, is charming and goofy enough to please even when the script isn’t quite so consistently amusing as its predecessor. But that’s still pretty damned funny.

Remember to stay seated for the elaborate, star-studded end credits sequence.