Cast: Michael Jackson.

THIS is it - the doco-concert film about the making of what would have been Michael Jackson's 50-gig swansong.

On the one (gloved) hand, it's a fascinating insight into what might have been - an amazing and potentially unrivalled stadium-sized musical experience and a fitting farewell to the King Of Pop.

On the other (ungloved) hand, it's also a privileged behind-the-red-curtain peak at the work that went into setting up this marvellous cavalcade of bar-raising tunes, smooth moves and impressive visuals worthy of Jackon's regal position in modern music.

That first (gloved) hand - the concert that wasn't - is handled deftly, despite an obvious dearth of material.

Through a handful of cameras of varying footage quality, we get to see Jackson, his dancers, his band and his backstage crew running through the show in the lead-up to opening night (which would have been July 13 - 18 days after his untimely death).

The film-makers have intelligently woven the prepared CG video backings into the uneven but still impressive performances. On the available evidence, the sequences for Thriller, Smooth Criminal and Earth Song would have been something special, and Ortega does his utmost to demonstrate this, with much success.

The behind-the-scenes bits are equally fascinating but this is also were the film falls down in a minor way.

While we get snippets of insight into the players and what the This Is It tour means to them, as well as the perfectionist nature of MJ as he puts everyone from the band to the lighting guys through their paces, there's one thing missing from the whole she-bang - MJ himself.

Yes, he's there on stage, ruling it like the King he was, but nowhere at all in the film do we get a decent idea of who he was as a person and what this concert project meant to him.

While it's difficult to know what ended up on the cutting floor (or wasn't filmed at all), you can't help but feel disappointed that Jackson is unwittingly portrayed as a mostly shadowy, unknowable and often distant figure.

Still, as a backstage glimpse and a thrown-together coodabeen concert, This Is It is unmissable for anyone who's ever attempted to moonwalk.