There are two kinds of time-travel movie, ones in which timelines are immutable - any attempts to change time invariably cause self-correcting mechanisms to prevent this, such as Twelve Monkeys - and others which are infinitely malleable timewarp fantasies such Back To The Future, in which changing events create alternate universes.

Instead of a setting such as Hill Valley in BTTF, the Terminator series uses a person as its logical fulcrum - John Connor, the future leader of the human resistance. It follows this with an optimistic message of hope for humankind's command of its future, which Cameron's splendid, if overlong, sequel reinforces and Jonathan Mostow's second sequel badly tears up.

Cameron sets his stage quickly and efficiently with a single title card - humankind is in a nightmarish future after an artificial intelligence assumes control of the world. "The battle for our future would not be fought there. It would be fought in our present. Tonight..." The Terminator is a "microchip-controlled hyper-alloy combat chassis" - in short a tough metallic skeleton, surrounded by living human tissue. It is indistinguishable from a man - and sent back through time to 1984.

The cyborg's program dictates that he must kill Sarah Connor, the woman who will give birth to humanity's saviour. Her protector is a man, Kyle Reese, also sent back through time and who may be barking mad.

The Terminator's methods are ruthless, bloody and efficient. "It can't be bargained with. It can't be reasoned with! It doesn't feel pity or remorse, or fear. And it absolutely will not stop, EVER... until you are dead!"

Arnold Schwarzenegger is well cast as Cameron's supreme realisation of the boogieman. His impressive physique, thick accent and minimalist performance - he speaks a mere 21 lines throughout - give credence to there being a machine behind the curtain. A cold, alien intelligence.

Michael Biehn's performance as Reese is also excellent, wringing pathos and drama from his character's unenviable predicament - and since he does not share The Terminator's amorality and invincibility, he has a much harder time. When he speaks of John Connor, it gives the subtle impression of a love affair; He tells Sarah "He has your eyes!", and that he'd die for him. Linda Hamilton as Sarah Connor doesn't have to do much, other than look terrified until the latter half of the movie. She grows on you however, and eventually gives the film its steel - finding the strength to resist and overcome the inhuman machine.

Visual effects, while inexpensive and occasionally obvious are highly effective and original. Cameron's designs translate well to clever model work and rear projection by Fantasy II to create excellent future war sequences. The titanic HK-machines (Hunter Killers) are unsubtle, streaming plasma firepower every which way which rends flesh into explosive smouldering matter. The guerrila trench warfare sequences are a bravura showcase of intrascene editing by Mark Goldblatt, his splendid cutting fashioning sense from chaos.

Brad Fiedel's synthesised score lends the machine its black heartbeat - a brooding electronic soundscape often used to stretch a tense scene to breaking point. Cinematographyer Adam Greenberg shoots using low-key and harsh lighting, concentrating on close-ups of Schwarzenegger's pitiless and terrifying eyes.

Speaking of eyes - there is superior prosthetic work by Stan Winston. A sequence midway through the film where the Terminator is conducting bloody repairs is gruesomely effective. Gargoyle shades disguise an icky eye exam, lending a brief moment of iconography. The makeup and false-limbs look as they should, both artificial and mechanical. These hugely creative technical skills are further refined and improved in Cameron's excellent Aliens, an $18million movie that easily looks double the price.

The Terminator is James Cameron's masterpiece. A lean, brooding, violent and unforgettable experience from a director hungry for success. The hunger is crucial for its power - a simple need to express himself whatever the means or cost. This mutated throughout Cameron's career until his reputation as a control-fiend became well deserved. It reminds me of what Robert Rodriguez films were like before he commanded $50million-plus budgets.

His script is smart, keeping the sci-fi ideas simple and doesn't waste a moment on superfluous plotting. He folds his screenplay into a surprisingly nasty amalgamation of horror film, brutally effective action flick, and doomed gothic romance. His great talent is in delivering a continuous stream of plot development on the move with unrelenting tension.

It is a model for others to follow.