The Mystery Of Edwin Drood: I'm the director
Charles Dickens died without finishing The Mystery Of Edwin Drood - in fact, he was only halfway through, leaving all the balls in the air and numerous hints, blind alleys, unrevealed connections and intriguing possibilities on display.
In short, a challenge not to be missed.
So, Gwyneth Hughes, a writer of great elegance, Anne Pivcevic (exec producer), Lisa Osborne (producer) and I enter weeks of intense discussions about how to bring this exciting and challenging work to the screen, not necessarily as Dickens would have done, because who knows what he intended, but in a way that remains true to most of what he did write.
And, about that ending... no, I'm not revealing that here! Be fair - this is The Mystery of Edwin Drood after all.
So what's it about?
Drugs and stalking certainly, which gives it remarkable modernity, and the moral and mental collapse of John Jasper (Matthew Rhys) whose obsession with 17-year-old Rosa (Tamzin Merchant) leads to his murderous plans for her fiancé, his nephew, Edwin (Freddie Fox).
It is a murder mystery started when the genre was in its infancy.
Casting proves a joy. Freddie (yes, another talent from that dynastic family) virtually casts himself as the golden-haired youth blessed with everything that Jasper hasn't, including, of course, Rosa.
Matthew, newly returned to us from his American fame in Brothers And Sisters, seizes on such a different project as the perfect reintroduction to the British television audience. He is a dark and brooding revelation and a joy to work with.
Then to cast a cathedral - central to the story. Rochester, Dickens' home turf, is the template for Cloisterham, and much is shot there around the town and its cathedral precincts, but the interior is changed beyond recognition and attention shifts to St Bartholomew's church in Smithfield, London, a gloriously gaunt, dark, romantic and magically untouched space.
Drugs affected our decisions in developing the photographic style. Not directly, you understand, as the BBC is unaccountably reluctant to fund my personal research into the effects of opium, but in deliberately manipulating mood through light and enhancing Jasper's different view of the world.
He is a man aspiring to the celestial while going to the bad, so we film him some of the time as if hanging between the dark and the light.
We make his fantasies under opium rich and indulgent, but when his world fragments, his dreams are shot in an altogether bleaker way.
But enough of that.
Being Dickens, the story is also full of humour and humorous characters.
Many a boy auditioned for the part, but none stole our hearts until Alfie Davis, aged nine, auditioned by mobile phone from his holiday in Spain.
With his dad filming him while reading in for the other characters and offering the odd whack round the head (scripted), Alfie proved born for the role.
So now it's done and the final verdict rests, as it should, with the viewer.
But I like to think that the governor himself, the extraordinary Charles Dickens, would approve even if, as seems highly likely, it wasn't what he intended at all.
We all had great fun second-guessing him and the finished films are agreeably recognisable as true to our original vision.
Diarmuid Lawrence is the director of The Mystery Of Edwin Drood.
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Watch the actor Matthew Rhys, producer Lisa Osborne and screenwriter Gwyneth Hughes discuss the contradictory character, John Jasper.
Comments made by writers on the BBC TV blog are their own opinions and not necessarily those of the BBC.