Wrong. Just one of many examples, given by a reader from England:
I grew up in the Inner Temple, London, and subsequently was educated at Westminster School. As a result, I had free and constant access to two of the scenes of the Da Vinci Code, and for this reason I can say with confidence that Dan Brown has either never been to the Temple and Westminster Abbey Chapterhouse, or did so long before he wrote his book and therefore had forgotten the geography.
From the Temple Church, the heroes of the story run to Temple Station, and from there take the underground to King's College. But (a) Temple Station is in fact the nearest underground station to King's College and (b) King's College is closer to the Temple Church on foot than Temple Underground Station is.
From the Chapter House at Westminster there is no direct connecting route to or from the Abbey. As in most monasteries, you have to leave the Abbey, walk along the cloister, and enter the Chapter House from there. There is no view over College Gardens (named after my old school which uses them for cocktail parties - incidentally the oldest lawn in the world).
This reminds me of something written by Dan Burstein, editor of Secrets of the Code. He wrote (and I paraphrase, because I don't have his book with me and I'm on the road) that Dan Brown is actually more accurate the further back in history he goes in The Da Vinci Code. But if you can't trust an author to be accurate about modern-day details that can be confirmed through direct observation, or via trusted resources (maps, travel guides, etc.), why trust him about ancient history? Weird.