The crazed slaughter of more than 800,000 members of the Tutsi tribe by the Hutu majority has most memorably been served in film by Hotel Rwanda.

That movie took an Oskar Schindler-like hotel manager (played by Don Cheadle) and showed how he saved lives thanks to persuasive patter and the covert use of his business as a safe haven.

British director Michael Caton-Jones eschews such devices and bases his story solidly on the real events of April 1994 at the Ecole Technique Officielle in Kigali.

The school - run by the Catholic church - became the refuge for more than 2,000 Tutsis as the random, radio-inspired killings around the city became more widespread.

However, they were left to their fate when a well-armed company of Belgian UN para-commandos were ordered out. About 2,500 men, women and children died in the resulting slaughter.

Co-written by BBC Newsnight reporter David Belton, this benefits from a straightforward, unflinching approach to yet another chapter in history where all human decency is notable by its absence.

Unlike the Nazi's final solution, this was no cold campaign of industrialised slaughter but an anarchic orgy of bloodletting carried out by moonshine-swigging, machete-wielding former neighbours of the victims.

Caton-Jones lends proceedings a human scale with the casting of John Hurt as the veteran priest who runs the school and an impressive Hugh Dancy as a young teacher facing the dilemma of whether to stay with his pupils (and face an almost certain death) or leave when the UN pull out.

The UN is represented by Belgian Capitaine Charles Delon, a compassionate man who bitterly resents being shackled by the Security Council's weasel-words - he's there to "monitor the peace" while the slaughter reaches fever pitch.

It's not an easy watch - one scene pans across the bodies of mutilated children and another the corpses of raped nuns - but it's never sensational or gratuitous.

Using the original locations (Hotel Rwanda was filmed in South Africa) adds a sickening frisson as does the use of real victims of the genocide as extras.

Don't go expecting clever narrative twists or fancy camera angles. But do expect to be reduced to tears of impotent rage.

Tim Evans