Douglas Adams' Dirk Gently: How slavishly should a screen adaptation follow the book?
It's been made very clear to me, mainly through conversations on Twitter, that a lot of people hold the Dirk Gently books in great affection and that they are going to be very upset if we don't get it right.
Dirk is described as "a pudgy man who normally wears a heavy old light brown suit, red checked shirt with a green striped tie, long leather coat, red hat and thick metal-rimmed spectacles".
Well, I'm a man; we got that much right. But I'm not that pudgy and I play Dirk wearing none of the clothes described.
Does that matter? Should they have scoured the country for a chunkier actor? I believe there are some out there.
Without the red hat is the whole enterprise doomed to failure? Is playing him without a green striped tie tantamount to dancing on Douglas Adams' grave?
A blond Bond? The books say he has black hair falling down over the right eyebrow!
It's a thorny old question - how slavishly should a screen adaptation follow the book?
Some people won't be satisfied unless the images they had in their head whilst reading the novel are translated exactly onto the screen.
But what most people want, I imagine, is that they enjoy the screen version as much as, if not more, than they enjoyed the book and that the spirit of the book is preserved - if not the thick metal-rimmed glasses.
You couldn't begin to do justice to them in a single hour of television. Too much happens, there are too many ideas.
So Howard Overman, our writer who knows a thing or two about writing for television, as any of you who watched Misfits will know, decided that if he was going to write an hour of telly then it needed to work as an hour of telly first and foremost.
It sounds obvious but you'd be amazed how often that isn't the priority.
Once that's established and you realise that you can't shoehorn the whole book into that time, you've got some decisions to make, what's in and what's out? What do we need to invent or add to make what's in work?
Once everyone's happy with the script, you cast it. Again, does it matter that I don't look like the Dirk that's described in the books? Is it enough that the actor gets the spirit of the character?
Dirk is one of the most interesting and complex characters I've played. He's charming, irritating, bright, funny, hapless, unreadable, transparent, roguish, chaotic, philanthropic and possibly dishonest.
If I get all that right, am I allowed to be too thin?
Television is a team sport, novel writing isn't. Our film has creative input from Howard, me, the director, the producer, the rest of the cast and dozens of others.
And all the stuff from the books that doesn't feature is still sitting there ready for us to use once the BBC commissions a 58-part series...
I'm extremely proud of how it's turned out. I hope you enjoy it.
Stephen Mangan plays Dirk Gently in Dirk Gently.
Comments made by writers on the TV blog are their own opinions and not necessarily those of the BBC.