As many actors have learned the hard way, you can't play a funny person: you genuinely have to be funny, or not. Emma Thompson is funny, and always has been: she got her start, in Cambridge Footlights revues, performing alongside the likes of Stephen Fry. But she doesn't much tap into her funniness as Katherine Newbury, the British host of a long-running American talk show in Late Night.
This is all the more disappointing given that Late Night is so plainly rooted in personal experience - though not so much the experience of Thompson or of director Nisha Ganatra (who, frankly, doesn't do much to differentiate the film from the average made-for-Netflix production).
Rather, the key player here seems to be screenwriter and co-star Mindy Kaling, who got her start as one of the writers of The Office, and who might be expected to know something about what being funny entails.
There are specific moments here that have the feel of being drawn directly from personal experience - or which at least convey something plausible about how the TV sausage gets made. This is true, for instance, of the scene shortly after Kaling's character Molly - an Indian-American woman who used to work in a chemical plant - clocks in for her first day as a writer on Katherine's show.
Immediately, she's faced with a gaggle of white men, ranging in age from early 20s to late 40s and in dress from preppy to sloppy, but merging from a distance into one homogenous group.
Less persuasive is the worshipful view of Katherine, a boss from hell who is also meant to be a class act: we keep hearing of her commitment to ''excellence'', not really a comedy word. Her humour is arch, raised-eyebrow stuff, aiming for smirks rather than belly-laughs, and wilfully out of touch with youth culture: a glimpsed headline cruelly but accurately dubs her ''America's least favourite aunt''.
Looked at one way, the premise of Late Night is pure science fiction: in reality, no woman has ever succeeded as a late-night host on US TV on anything like this scale (Joan Rivers lasted seven months, which shows the magnitude of the problem). In this sense, the film feels like a strategic conversation-starter - a dramatised think-piece about identity politics in the media, taking care to cut across conventional wisdom while still hitting all the standard talking points (though unlike in the real late-night world, nobody references Trump).
At least Kaling has the knack for writing characters who have two dimensions rather than just one, allowing scope for lots of good performances around the edges. Ike Barinholtz is appallingly plausible as an obnoxious ''bro'' comic being groomed to replace Katherine, and John Lithgow is at his gentlest as Katherine's dying husband, though he drops enough hints to let us imagine the different man he might have been in the past.
Ultimately, part of the point of Late Night seems to be that Katherine and Molly are twin souls - both depressive workaholics, both rigid and awkward personalities in general. Whether two such people would do each other much good on any level is open to question. Still, I'm willing to accept this as an accurate picture of how comedians can be - which is not to say that the accuracy makes Late Night any funnier.