The name "Will Ferrell" and the word "understated" wouldn't normally appear in the same sentence...let alone the same film.

Yet, here the less-than-subtle star of Talladega Nights and Anchorman weighs in with a performance of real poignancy and poise.

He plays US tax inspector Harold Crick, a dull drone uneasy out of his rigorous routine and prone to obsessively calculating mundanities such as the seconds taken to reach his bus-stop.

Then, suddenly one day, he overhears a woman's disconnected voice providing an exact commentary on what he's doing - and what he's about to do.

It transpires that Harold is the unwitting main character in a novel being written by Karen Eiffel (Thompson), who has hit writer's block regarding how to kill him off.

Now, if you can accommodate this conceit, then Harold's subsequent fate takes on an excruciating resonance as he finally wakes up to his threatened life's possibilities.

The catalyst for his emotional enlightenment is Gyllenhaal, a flighty, flour-streaked baker who refuses to pay that proportion of taxes that funds military hardware.

Initially, Crick is her by-the-book persecutor, chasing her for the unpaid tax, but he becomes entranced with her carefree worldview and finds himself falling in love.

The lynchpin of this beguiling story is the chemistry between Gyllenhaal's bright-eyed free spirit and the understated - yes, that's right, understated - Ferrell's buttoned-up jobsworth.

Director Marc Forster (Finding Neverland) has fashioned an unconventional rom-com of a style that will be familiar to fans of Charlie Kaufman (Eternal Sunshine of the Spotless Mind, Adaptation).

Once you've bought into the concept, there's plenty to enjoy as Harold discards his hang-ups (one scene where he warbles Wreckless Eric's Whole Wide World is worth the entrance fee alone) and desperately tries to find a way to escape his literary fate.

Deliciously different, it's a neat riposte to Benjamin Franklin's assertion that the only two things in life that are certain are "death and taxes".

Tim Evans