IT'S amazing to think that almost five years have passed since the events of 9/11.

Oliver Stone's World Trade Center, starring Nicolas Cage as a fireman who helps with the rescue, is released later in the year but first up, we have this harrowing movie from British director Paul Greengrass.

Greengrass, who began his career working on ITV's World in Action, is known for his work on controversial subjects like the Omagh bomb and the Stephen Lawrence murder. And now he has produced one of the most accomplished pieces of film-making I think I've ever seen on a cinema screen.

United 93 works because of what you know, and what you don't know.

The first part concerns the fate of the passengers on the titular flight, which was one of four hijacked by Islamic extremists on that awful morning.

The common knowledge is that three planes hit their targets of the World Trade Center in downtown New York, and the Pentagon.

The fourth plane crashed outside Pennsylvania, the passengers having realised they were on board a suicide mission and apparently acted to prevent the plane from reaching its target of The White House.

But what we're not so aware of is the extent of the failures on the part of air traffic control and the US military to act.

We spend what is perhaps the majority of the film in control rooms watching initial confusion evolve through frantic phone calls into chaos and desperate panic, realising that these top-level people only knew what was happening thanks to American news channel CNN.

Greengrass' movie unfolds in real time, which lends an unbearable tension to events.

It feels like an age as you're waiting for the impotent powers to engage, almost screaming aloud in frustration as they try to work out what's happening with these planes which suddenly drop off the radar.

Our terrible knowledge of how this story ends bears down on an audience throughout, making scenes where passengers phone their families from on board, saying goodbye, very tough to watch.

When things finally erupt into chaos, it's terrible to behold.

The cast of unknowns are pitch perfect so good, in fact, that it's hard at times to remember that this is a recreation of events.

The script was based on actual recordings, transcripts and detailed interviews with all of the bereaved families, and, as such, feels wholly authentic and appropriate to every moment.

There's nothing overtly sentimental or gratuitous thrown in for effect.

As you watch, you'll be both angry and aghast at the lives lost in the name of apparently opposing gods, watching cold-blooded murder arise out of fanaticism, and remember our own tragedy, 7/7.

Most ordinary people on that dreadful day could only stand helpless in the face of the almighty rage generated by said fanaticism but not these passengers of United 93.

This is strong stuff, not to be missed, under any circumstances.