A mismatched party of two stirs up the Group of 8

“The Girl in the Cafe” (premiering Saturday on HBO) is a somewhat schizophrenic, mostly satisfying romantic comedy from Richard Curtis, the author of “Four Weddings and a Funeral,” “Notting Hill” and “Love Actually” (and also the director of the last). The story of an aging junior government official and the young woman he meets in a cafe on his lunch break, it’s of unusually high quality for a TV movie, from its natural-sounding dialogue to its unobtrusively elegant photography, and for most of its length, it is somewhat more realistic than a typical Curtis film -- which makes its missteps all the more disappointing.

As far as the actors are concerned, I couldn’t be more pleased if I had cast it myself. Bill Nighy, who has worked with both Curtis and director David Yates, plays Lawrence, who works for Britain’s chancellor of the exchequer (Ken Stott) and has nothing to show for his life but his job. Nighy may be the Hardest-Working Man in British Television, popping up what seems like every other week in some imported production on BBC America or PBS. His small-screen credits include “State of Play” (directed by Yates), “The Lost Prince,” “The Young Visiters,” “Longitude,” “The Canterbury Tales” and “He Knew He Was Right,” and on the big screen he hilariously played a washed-up rock star getting his second 15 minutes of fame in Curtis’ “Love Actually” and can be seen as Slartibartfast in “The Hitchhiker’s Guide to the Galaxy.” If there were a cable station devoted exclusively to him -- All Day, All Nighy -- I would be first in line to subscribe.

Long and lean, with a mop of thinning hair and a snorting laugh he carries from role to role, Nighy has played a wide range of characters with only the merest adjustments of his native body language. For Lawrence, he’s added a kind of scuttling walk and a habit of deferential physical contraction. Only marginally less inward is Kelly Macdonald’s Gina, the titular girl in the cafe. You don’t notice that she’s a mystery until Curtis wants you to; it’s a nice bit of misdirection. Macdonald, who is possibly best known to American audiences as the Nancy Drew figure in “Gosford Park,” worked with Nighy and Yates in “State of Play.” She is small and compact, and is the sort of actress who is so good that you always think she’s playing herself, however different her parts may be.

Lawrence and Gina, having plausibly met and conducted a halting but humorous conversation over their hot drinks, meet again, and as daring leads to daring, he asks her to accompany him to the Group of 8 Summit in Reykjavik, Iceland -- where, because he’s neglected to book her a room in advance, they become roommates. The film asks two questions: Will they sleep together? And will she cost him his job? For once she’s among the ministers and minions, and primed by Lawrence with facts and figures as to the human cost of poverty, she reveals an inability to keep from speaking truth to power.

The echoes of “Lost in Translation” -- a May-October quasi-romance, set largely in a clean-lined hotel in a strange foreign place -- are strong enough to seem intentional, as if Curtis had it in mind to work out an alternate future for its protagonists. But the real program here is political: Curtis, a co-founder of Comic Relief, is involved with the Make Poverty History campaign, whose goals the film has been made to advertise.

The film also celebrates Britain’s current captaincy of the G-8, and its premiere has been roughly timed to the opening of this year’s meeting. “Girl” reflects the official focus on African poverty, debt relief and fair trade. Curtis is a sort of British Anglophile, and the Brits -- as represented by Stott and by Corin Redgrave’s prime minister -- are the heroes here, fighting the “Let’s get this over with and move on to something we want to talk about” bullying of the American delegates, with Macdonald representing the People’s Truth that justice is simple.

I appreciate his themes -- that there is no wrong time to speak out, that a butterfly beating its wings in Reykjavik might cause money to rain down in Africa -- but the more Curtis wants to make his point, the more his script pushes the bounds of believability. It requires powerful people to act very differently from the way powerful people usually do. It hijacks its almost-lovers into the service of a predetermined end and suddenly turns what has been a first-class romance into a bit of second-rate propaganda. (Frank Capra could get away with this stuff, but just barely.)

It’s not exactly a fatal derailment, though it leaves a funny taste -- like being asked out on a date only to be hit up for a donation. For the most part, it’s an intelligent good time. It’s interesting that Curtis, who was one of the brains behind the gleefully cynical “Black Adder,” should have become such an old softy, the Nora Ephron of the Blair generation. But he can write a joke and craft a character.

Bill Nighy completists will, of course, find the film nothing less than essential viewing.

*

‘The Girl in the Cafe’

Where: HBO

When: 8 p.m. Saturday

Ends: TV-14 (may be unsuitable for children under 14)

Bill Nighy...Lawrence

Kelly Macdonald...Gina

Ken Stott...Chancellor

Anton Lesser...George

Corin Redgrave...Prime minister

Executive producers Paul Abbott, Richard Curtis. Director David Yates. Writer Richard Curtis.