To date, the Harry Potter films have more hold on the collective unconscious – not to mention box office clout – than they necessarily deserve. JK Rowling’s billion-dollar literary creation may have a killer hook in any medium – a subterranean magical realm beneath our own workaday world – but the what-happens-next urgency that characterises her work on the page has rarely translated onto the big screen. Indeed, only Alfonso Cuarón’s Harry Potter And The Prisoner Of Azkaban has actually got it right.

The rest of the Potter canon, for all the attendant hysteria, has made for indifferent cinema. Cluttered with too many diversions and incidental details, the franchise has never seemed to learn that while tangents may be rewarding for the patient reader, out here in the movieverse, things are different.

Unless we’re watching a Jim Jarmusch film, we don’t want tangents, we want action, action, action. Action, alas, is something that Harry Potter And The Half Blood Prince lacks in spades. This is no fault of director David Yates who works exceedingly hard at making a decent romantic teen soap out of a book, which, like most of the one that comes immediately after, is merely a holding pattern.

Write down everything that happens and it looks like this – Harry likes Ginny and Hermione – now a total young battleaxe, think Apatow wife – likes Ron.

Happily, The Half Blood Prince is an improvement on the last installment; those legions of British actors playing wholly unnecessary supporting characters have been sent packing and the impulse to cram in every superfluous comma in order to appease the fans – call it Watchmen Syndrome – has given way to neater narrative lines.

Smart viewers will know this is only the first of two-and-a-half movies in which we are doomed to sit twiddling our thumbs in anticipation of the final showdown with Voldemort. Oh well. That’s only about 17 more hours to go.