‘Brutally unfunny.” “Lacking in charm and good jokes.” “As interminable as it is revolting.” The reviews have not been kind to The Nan Movie, which stairlifts Catherine Tate’s alter ego to the dizzy heights of the big screen. The film finds Nan – aka Joanie Taylor – road-tripping to Ireland with grandson Jamie (Mathew Horne) to visit her dying long-lost sister. Spliced into this story are flashbacks to the second world war, when Joanie and Nell (Katherine Parkinson) courted, and fell out over, the same GI – which explains, apparently, the embittered geriatric the character has since become. The most interesting thing about the film is probably its production history. Plan A, according to recent reports, was that it focus on the wartime backstory which, as it survives in the released film, is told in a totally different, more dramatic register than the broad comedy of present-day Nan. Somewhere along the line, the road-trip framing device spread across the whole movie. That’s a shame – for viewers, because the two strands (and the two versions of Nan/Joanie) feel very mismatched, and for Tate, whose original concept (if those reports are true) represented a more interesting answer to the question: what to do with Nan next? Nan is, after all, Tate’s breakout character, the only one from her hit noughties sketch show to enjoy a substantial afterlife. There were the TV specials, which saw Nan fight off property developers, join an anger management class and entertain a visit from David Tennant’s Ghost of Christmas Present. There was Nan’s leading role in Tate’s excellent 2016 stage show. But what next? As the trajectory of, say, David Brent suggests, audiences are up for coming on a lifelong journey, across different media, with their favourite comic characters – as long as their creators find fruitful new contexts and challenges for those characters to surmount. The supreme example is Alan Partridge, with whom Steve Coogan hits the road next month on a new tour. Having navigated successfully from his origins in a TV news spoof via sitcom, books, stage shows, a podcast and a movie – then back to a TV spoof again – Partridge will probably still be amusing us in his dotage. Key to his across-the-decades success is that very variety of contexts in which Coogan has situated the character. It matters, too, that the persona was so rich, fruitful and true in the first instance. Nan’s a great character, too – if more one-note than Partridge, and overly dependent on the frisson generated by an elderly woman effing and blinding. But the key disadvantage Tate faces in developing the character is that Nan is already old. We as the audience can’t watch her grow (she’s at least 100, going by the film’s improbable chronology). Small wonder that a movie telling her backstory (watching her get younger, in a sense, rather than older) felt like a good next step. You could argue that another of the nation’s best-loved characters, Count Arthur Strong, is in a similar boat. Steve Delaney has been performing Arthur for over 20 years. He never stops being funny, but he doesn’t (can’t?) develop – give or take the slight shifts in emphasis, and degrees of lunacy, in his TV versus his stage incarnations. Both performer and audience get a whole new type of comic experience, and the chance to sound new depths of laughter and emotional significance, when we shadow a character across the span of their lives. That’s what Tate tried to tap into with The Nan Movie, and it hasn’t quite worked. That’s what fans will be looking forward to – alongside the jokes of course – when Coogan steps out onstage as Partridge again, his first live appearance in a decade, in a month’s time.