At the optimistic end of 2018, four excitable Derry Girls and one perplexed wee English fella burst into our lives and made for one of this year’s televisual highlights. Located in a “troubled little corner in the north-west of Ireland”, the mile-a-minute Channel 4 sitcom was loosely based on writer Lisa McGee’s childhood during the Troubles, when Sinéad O’Connor posters adorned bedroom walls and there was not a mobile phone in sight – just people living in the moment. Oh, and armed soldiers were non-speaking extras in daily life.

In tandem with director Michael Lennox, McGee found the humour in this unique situation with an authenticity that made us feel like we could have been there. Everyone had pals like Michelle (Jamie-Lee O’Donnell), the coarse firebrand (“I’ve been thinking, it might be time to lose the rest of my virginity,” she mulled in preparation of a party), her English cousin James (Dylan Llewellyn), who’s the butt of every joke, Clare (Nicola Coughlan) who likes to play by the rules, Erin (Saoirse Monica Jackson), a simpering ball of righteous teen angst, or Orla (Louisa Harland), who’s just as much of a free spirit as her mum, Aunt Sarah (Kathy Kiera Clarke).

Those are only the protagonists. There was also a cast of meticulously acted secondary characters – such as the wonderfully cynical Sister Michael (Siobhan McSweeney), who really should neither be a sister nor a teacher. (Sample assembly announcement: “I know how daunting resit examinations can be. So if anyone is feeling anxious or worried, or even if you just want to chat, please please do not come crying to me.”) Throw in Inbetweeners-style situations we all encountered at school – such as the flurry of hormones when exchange students came over en masse – and the Derry Girls’ world became ours, too.

Sister Michael from Derry Girls. Photograph: Channel 4

Its universality was just part of why it became Channel 4’s largest comedy launch in five years – a second series is in the bag ­– and is sitting pretty on Rotten Tomatoes with a 100% rating. If the Smash Hits-level of 90s music wasn’t enough to take a generation of viewers for a nostalgia trip, there was also the ending. Not since the moment when Denise Royle went into labour had there been a more poignant scene in a sitcom than the one in which Granda Joe (Ian McElhinney) laid a supporting hand on the shoulder of Gerry (Tommy Tiernan) as they watched news of a bombing.

And therein lies the reason for Derry Girls’ increasing momentum throughout 2018. For all its humour, it possesses a gravitas that other nostalgic teen comedies do not.

Most likely, the show’s underlying intention was to highlight that by hook or by crook, life went on in Derry in the days of civil unrest. But it also serves as a timely reminder of Dolores O’Riordan’s ethereal vocals in the year of her death, with Dreams by the Cranberries bookending the series. And it made the political personal at a timely moment. With the border question featuring prominently in the Brexit negotiations, the last episode helps put that into context: no one wants to return to tragic deaths within the community while nearby, kids are trying to be kids, dancing terribly to Madonna on a school stage. It’s such a force that a campaign group named Derry Girls Against Borders has assembled, made up of everyday folk who are keen that life in Northern Ireland continues as is.

But even without its unintended political relevance, the alchemy of the setup –­ from the whip-smart script to its authentic production ­– suggests that there’s plenty of enjoyable telly-watching hours to be had in Derry yet. And more screen time for Sister Michael, please.