At first glance, William Shakespeare's The Merchant Of Venice would seem an unlikely candidate for a big-screen treatment. An unwieldy blend of romantic comedy and tragic melodrama, this 'problem play' has to clear an additional hurdle in our enlightened times thanks to its characterisation of Shylock, the Jewish moneylender who seeks a literal pound of flesh from his Christian nemesis. Michael Radford's gloomy film is a long and slightly draining haul, but the intensity of Al Pacino's central performance justifies the effort required.

In Shakespeare's time, Shylock was played as a crude, anti-Semitic caricature. Radford's film, however, offers a far more contemporary interpretation, with the Jew's scheme against Jeremy Irons' Antonio motivated by an outsider's sense of injustice and persecution. Irons, too, has a psychological burden to carry as his merchant's decision to indebt himself to Shylock is a result of his unspoken homosexual lust for Joseph Fiennes' fortune-hunting playboy Bassanio.

With the latter off courting the fair Portia (played by newcomer Lynn Collins, whose uncanny resemblance to Gwyneth Paltrow, Fiennes' Shakespeare In Love co-star, can hardly be a coincidence), Antonio must face the music as Shylock demands his bloody forfeit in court. The trial scene is the centrepiece of any stage production and is no less effective here, with Al's implacable avenger chillingly unmoved by the disguised Portia's eloquent protestations.

"OPPRESSIVELY SOMBRE AND TORTUOUS"

Radford's decision to keep faith with the play's 16th-century setting pays off in authentic Venetian locations and a painterly use of light and shadow. But the oppressively sombre mood and torturous pace make this harder work than it should be, with Pacino's melancholy presence dominating proceedings long after his premature exit. The movie is worth catching on the strength of his work alone. Despite this, you can't help thinking it will confirm more prejudices about filmed Shakespeare than it confounds.