Some rate THE NINE TAILORS as Dorothy's best "Lord Peter" novel. It is certainly very good, but I like GAUDY NIGHT for that encomium. Well, no matter, this BBC film may be the best in Ian Carmichael's 5 film series. It has quite a bit going for it, including giving one a chance to hear what the cacophony of change ringing really sounds like. There's some nice camera glimpses of the "Fen Country" of eastern England, spotted with a generous selection of local characters excellently portrayed by BBC's cast. The introductory material is good of itself. In the novel, most of what we actually see here is related in conversations and interrogations. BBC shows the action taking place, with the result that Ian Carmichael plays young "Lord Peter" as a subaltern about to ship over the channel to take part in The Great War, and the adult 15 or so years later, solving a mystery that had its roots in the wedding party he attended in 1914! We also get to see "Sgt. Bunter" rescuing "Major Wimsey" after he was buried when an artillery shell scored a direct hit on his dugout. Later, we see "Bunter" applying for the job as his lordship's valet, and getting it. It's a very effective adaptation.
Dorothy's tale as it unfolds in THE NINE TAILORS is a complicated one, which it is almost impossible to discuss without giving away plot elements important to beating "Lord Peter" to solving the mystery. I will say nothing beyond that it reminds me of many of Ross MacDonald's "Archer" novels, all of which involved events of usually many years previous to the current mystery, and which were responsible in good part for those current events.
Oh, what was Dorothy's egregious error relating to change ringing? Well, the rules are strict that the ringers who start the peal must complete it without any help or relief. Otherwise,the "record" cannot be certified. Vicar "Venables" stood in for several ringers during their 9 hour peal.