One of the best things that Mark Thompson did in his brief stint at the head of Channel 4 was to kill Brookside.

(Brookside, in case you don't know, had become easily the worst soap on British TV, but it was the only soap I ever really followed, and its death was a mercy killing, I was so glad to have it put out of my misery).

What has this bad, axed British soap got to do with Dan Brown's blockbuster novel 'The Da Vinci Code'? Well, in Brookside, in order to spin out some tedious plot-line over several episodes, actors would act with astonishing stupidity. They would do things so dumb that no-one in real life, not even really really thick people, would do. Say someone breaks into their house and steals something - they don't call the police, they fire-bomb someone else's house. Not the thief's. Just anyone's. Or it might just be a small-scale thing, a stupid and totally unneccessary lie that spirals out of control, with tedious consequences.

Now, the Da Vinci Code is a great book. Never has a page-turner turned so fast through my fingers (well, not since The Little Friend by Donna Tartt, and that because I wanted to find out who killed her brother. Gee, thanks, Donna).

But there are two stonking examples of what I call "Brookside Stupidity" in the Da Vinci code that spoil the book for me.

Remember the two central characters, Sophie and Langdon, are amazingly erudite, clever people. He is an academic, an expert on symbolism, and she is a cryptanalyst, and, as anyone who knows anything about Bletchley Park knows, cryptanalysts tend to be frightfully clever people, usually the brightest people in the country.

So, when they are in the bank, why are they TOTALLY flummoxed by the request for a 10-digit PIN number, when her own grandfather's corpse was found next to, er, a 10 digit number?

And why can they not see, instantly as I and I'm sure most readers did, that the script clue in the cryptex is simply in mirror writing?

Maybe Dan Brown is trying to make his readers feel smart, but it just made me think that the book was stupid.