Mark Thompson is quite clear about what his (modestly) titled Spectacular Show isn't: "It's not a science lecture," he insists. "It's all about having a bit of fun with science." Though, obviously, it's fun with a "Don't try this at home" caveat, at least regarding some chemical reactions shown during the show. Science, he warns us all on several occasions, should be treated with respect— as the slight whiff of burnt man-hair reminds us!
He believes the important thing at this point is the attention-grabbing spectacle.
Yes, there's an educational aspect to the show, in that Thompson explains some of the basics of physics: that electrons repel each other; that some gases are lighter than air, and inert; that air pressure changes depending on how fast or slow air is moving. Thompson doesn't particularly go into details: after all, the average age of the audience was probably around six-years-old! You get the feeling that he believes the important thing at this point is the attention-grabbing spectacle, and connecting the "science" to things children can easily relate to in their world.
Arguably, that's why the most successful displays involve everyday objects rather than complex mechanisms showing different sound wavelengths in a line of flames. (On the day of this review, the kids around me seemed pretty confused by Thompson bringing out his stylophone, while some of the grown-ups wriggled uncomfortably with their own spoiled childhood memories of Rolf Harris.) In contrast, across the board there seemed a genuine wonder at the water-absorbent crystals commonly found in babies' nappies, and real surprise when Thompson spectacularly showed us just how much stored energy there actually is in an individual jelly baby.
Thompson is an engaging figure on stage, though consciously always a grown-up, rather than a sugar-rush CBBC presenter. As to whether such shows encourage any real interest in STEM subjects (Science, Technology, Engineering and Mathematics)... well, until someone starts keeping academically-defensible records over the long-term, it's surely not an unreasonable conclusion that they're unlikely to do any obvious harm. Especially given the many excited kids I saw leaving the venue afterwards.