You’d be forgiven for not remembering Terminator 3: Rise of the Machines, since the two most recent installments in the franchise forgot it too, but if you do you may remember some pretty impressive action scenes accompanying the same rusty time-traveling robots. Thankfully the DVD includes a helpful audio commentary from the cast and director, which peels back the living tissue revealing the mental endoskeleton beneath.

It’s easy to see why someone thought Terminator 3, with its high aspirations, was worthy of the commentary treatment. And thanks to this unsung hero we’re treated to exclusive anecdotes about how a department store let them film a department store scene in it, how stars Claire Danes and Nick Stahl bonded over their childhood acting experience (which Danes audibly learns for the first time while recording) and how phone scenes are hard to film because you have to pretend there’s someone on the other end.

Arnie clearly has his mind on politics, with segments that are not so much commentary as filibuster, as he painstakingly describes how he got each individual muscle to the size it was in the original Terminator film, even though they’re clearly not. In fact the only time he gets truly animated is when describing the naked T-X, the female terminator, and how she’s able to enlarge her breasts.

His other main interest is the action, with his insistence on a costly crane smashing sequence going some way to explaining why they had to skimp on the director and supporting cast. The other unspoken reason is Schwarzenegger’s own record-breaking $30million fee, and contract which included round-the-clock limos, $1.5million for private jets and a fully-equipped gym trailer – the kind of genuinely interesting detail which is omitted.

Director Jonathan Mostow got the gig after Ang Lee turned it down to direct Hulk (what does that tell you?), and he and Danes are the only two to be together for the recording. With this in mind it’s astounding how she’s willing to constantly deride the film and the direction she received. She mentions that she was hired a day before filming began, explains how Mostow left her and Stahl to work out the parts on the job, and doles out back-handed complements, repeatedly referring to her co-star as ‘available’.

She doesn’t even seem to know the name of her character and is clearly trying to distance herself from the project. But after two hours anyone listening will want to be very distant from any project Danes is working on. If she started at my office I’d quit on the spot. Mostow, for his part, describes the most fundamental aspects of directing as if they’re enlightening pearls of wisdom, cheerfully admitting to not really caring about the characters.

The only person who seems to have enjoyed themselves is the T-X herself, Kristanna Loken – a model who loved having the opportunity to kick Arnie’s ass. And the one person who really outdoes themselves on the film and would be interesting to hear from – practical effects master Stan Winston – is not featured.

What’s remarkable is no-one seems even slightly interested in the mythology or to respect the fact they’re continuing a wildly popular franchise. But it does show what good actors Danes and Stahl are, since through their obvious antipathy offscreen and general contempt for the project they still manage adequate performances. It’s not surprising no-one was back for Terminator Salvation, and by the end of the commentary the most impressive thing about the film is that it reached the level of mediocrity it did.