Other inspiration: London Falling, by Paul Cornell
I stumbled across the book London Falling by Paul Cornell. It's very similar to Rivers of London: urban fantasy, police procedural, set in modern London, magic based on sense of place, magical world hidden from the mundanes, etc. But the tone is different. Where Rivers of London is a relatively optimistic book, London Falling has a distinct bend towards horror.
It's pretty good. It starts with a purely mundane police operation to take down a drug lord, and takes a bit too long to get to the supernatural side which is when things get going. The author switches viewpoint character rapidly, which can be a bit confusing especially as some of the characters aren't that strongly drawn.
I picked up the first book when it was on offer on Amazon, but sadly that's passed. It's the first book in a trilogy, and I'll pick up the other books at some point.