‘Here’s your new Sunday night obsession...’ the BBC announcer purred, overintoned and mini-orgasmed, like she was doing an audition for a Cadbury’s Flake commercial, ‘... a dazzling drama with a stellar cast.’

My hackles rose. Did no one ever mention to her the rule about ‘show not tell’? And my hackles were right. His Dark Materials has indeed become my Sunday night obsession: how can the BBC’s most-expensive-ever drama series possibly look, sound and feel so clunkingly, God-awfully, disappointingly flat?

Yes, I know Philip Pullman’s trilogy is an extended, bitter rant against Christianity disguised as children’s entertainment. But I loved reading those novels, especially the first two, which may be meandering, obscure and mawkish in places but are nonetheless thrillingly imagined, deliciously dark and hauntingly evocative. When I finally saw the magnificence of Svalbard, I found myself thinking: ‘So this is where Iorek Byrnison lives!’ — and neither book nor landscape felt wanting in the comparison.

But this HDM, to judge by episode one, is going to be as exciting as a grey fortnight becalmed in the doldrums with no wifi or cards or Pass the Pigs. Characters and settings appear with the same names they have in the books but it all feels perfunctory, done by numbers and slightly rushed. There’s no one — not even Lyra — that you can properly inhabit; the script is by turns leaden and, when it’s not being crudely expository, mystifying; the overblown score is dire. It just feels like odd, not particularly well-drawn or sympathetic individuals being manoeuvred, like chess pieces, through events which though exotic leave you cold, confused and bored.

Since Pullman gets a production credit, I can only assume he’s on board with this travesty. My guess is that, a bit like J.K. Rowling — who decided way after the event and contrary to the evidence in the entire Harry Potter series that Hermione is in fact black — he wishes that his books could have been a bit more woke than they actually were.

So, in this TV adaptation, the master of Jordan College, Oxford is black and so is the King of the Gyptians. ‘This is fantasy,’ the defence will no doubt run, ‘so there need be no constraints on our near-compulsory colour-blind casting practice.’ Maybe, but is it really true to the vision of the books most of us read in the early Noughties? The Gyptians, for example, were patently Romanies — and gypsies by birth, rather than lifestyle choice. By interspersing them with black characters it makes a nonsense of one of the book’s most colourful plot strands.

Even ten years ago a blockbuster BBC adaptation would have acknowledged this with quintessentially Romany sequences redolent of My Big Fat Gypsy Wedding, or a Guy Ritchie movie, or the outrageously bling Sinti family in Suburra. Now diversity casting has shoved its oar in — and had the counterintuitive effect of making everything look less diverse and more homogenous. I dread to think what they’ve done with the Armoured Bears: have they perhaps shoved in a few grizzlies to make them look less oppressively, uniformly white?

That blockbuster BBC adaptation of yesteryear would also have been much, much pickier about its casting. It would have been like Game of Thrones: every player a star, often with a solid stage career behind them. But here, apart from Ruth Wilson’s nicely ambiguous, seductive yet horrible Mrs Coulter, it’s hard to find a performance (and this includes James McAvoy’s Lord Asriel, sadly) which is better than average. And some are absolute stinkers. As someone said on Twitter, it feels like an Islington school production, only done with a bigger budget.

Not that you can actually see much of that budget. Sure, the CGI daemons (in Pullmanworld everyone has their animal familiar) are cute enough, but the aerial view of a flooded Oxford at the beginning looked like a video game landscape from about 20 years ago, before they nailed realism. Nor do I understand the stylistic inconsistencies: Lord Asriel landing in Oxford by a recognisably contemporary helicopter in the opening scene; then, just 12 years later, inhabiting a world which has suddenly come over all steampunk, with airships redolent of a retro-futuristic 1930s (something the unfairly maligned movie The Golden Compass captured so much more satisfyingly than this effort).

We are, I fear, fast reaching the point when the initials BBC attached to any drama production no longer serve as a badge of quality but as a warning flag. Glancing — all I can bear — at World On Fire, it may be that we’ve passed that point already. Then again, Dublin Murders still has me hooked; and Giri/Haji is pleasingly strange (and I particularly love Will Sharpe’s half-Japanese rent boy character). But the best is long past and ahead looms only disappointment and eventual irrelevance.