ON A shopping trip recently, I was indulging in my favourite game of “guess the person’s background by the contents of the basket”. This time, there was a strange addition to more than half the trolleys: the new Harry Potter book.

Everyone seems to own a copy. You’ll even see teenagers trying to get to grips with it in your local WH Smith. They are the ones shaking it and asking the assistant how it works and whether they can have it texted to their phone. The book is as likely to be bought by somebody on a two-for-one offer with Kerry Katona’s autobiography as by children whose mummies waited for them in the Range Rover outside Waterstone’s at midnight recently.

Unaccountably, a lot of the queuing customers who were dressed as wizards seemed to be adults. These are the sort who memorise Star Trek episodes and have been told by friends to get a life, read a book and find a girlfriend. One out of three is a start, I suppose.

If you were being snobbish, you might guess that Harry Potter is often read by adults who don’t read much. A colleague once told me: “JK Rowling describes people who have been turned to stone as having been ‘petrified’ what a wonderful, inventive use of language.” When informed by other staff that this is what “petrify” means to turn to stone she seemed nonplussed.

Teachers love children to be interested in reading, but the ubiquity of Harry Potter means parents will be getting their child to bring in their copy on the first day of the autumn term. Teachers will face eight-year-olds (whose last completed read was Kipper) staring at the mass of text for the next 20 quiet reading sessions. “What’s it about so far, Brandon?” “A wizard, Sir.” “What’s his name?” “I haven’t got that far yet, Sir.”

I’ve read the first book (a pleasant enough read) but I’m put off by the increasing size of the sequels, which most primary pupils barely have the strength to lift, let alone read. At least when they get bored by page 300 we can switch them to something exciting like The Worst Witch (about a school for witches hmm, that sounds familiar).

Another thing puzzles me. JK Rowling is so rich that she could spend her days flying around Windsor Castle in a gold-plated helicopter, screaming “I’m catching up, Liz!” through a loudhailer. Yet every time I see her on television, she looks more miserable than a group of heads at a target-setting conference.

Just enough space for me to give away the ending. Ofsted puts Hogwarts in special measures for taking the “enjoyment” part of “excellence and enjoyment” too literally. Inspectors aren’t happy with the lack of completed risk assessments, either. And quidditch is finally replaced by a non-competitive sports day.

More from Henry in a fortnight