The pairing of Keanu Reeves and Charlize Theron – last seen, to disastrously compelling effect, in 1997’s The Devil’s Advocate – must have been deemed a success by some deluded boardroom exec, since they have now been unleashed on us again for a fluffy romantic comedy with even less to offer in the grey matter stakes. Sweet November is exactly the sort of straight-to-video sleepwalker Irish director Pat O’Connor (Circle of Friends) was always destined to end up churning out for a living, and it’s sure to strike a resonant chord with sad no-lifes everywhere.

It’s an unappetising mix of Mills & Boon sentiment and yuppie vacuosity, with the unimaginative plot pitching obnoxious workaholic ad-exec Nelson Moss (Reeves) and bland nonentity Sara (Theron) together. The ingenious twist on which the film hangs is that they have settled for a one-month trial relationship, after which they will happily go their separate ways. But of course, they haven’t planned on falling in love...

The pair proceed to drag one another down to ever greater depths as the film gains momentum, spending most of the time grinning idiotically and trading snatches of inane dialogue with delusions of wit. As a result, Sweet November frequently plays like a lobotomised Hepburn/Tracy outing, with embarrassing stabs at goofy humour missing the mark all over the place. The situation isn’t exactly aided by Keanu’s complete inability to inject any intonation into his sentences: his relatively effective performance in The Matrix might have led us to forget exactly how awful he is, but this tour de force of total emotional expressionlessness serves to hammer home a chilling reminder.

Theron is her usual thrilling self, as might be expected: alternately smiling or pouting as the plot demands, but never remotely compensating for the vast black hole of personality and charm that blights the movie’s aspirations to some sort of romantic poignancy. A cute lickle eleven-year-old kid and a camp cross-dressing Jason Isaacs are roped in to provide unimpressive comic diversions, but only serve to make matters worse, and Sweet November drags on and on and on without mercy for two hours of unrelieved tedium. Rarely, if ever, can the closing credits of a movie have provided such a source of primal joy.

As sweet as a pig’s heart wrapped in barbed wire, this must be shunned by everyone with a functioning brain.