Wow. This is wonderfully, blissfully creepy, and the ending is just the right sort of conclusion. I love that here, it's a reversal of ghosts, and this perception of RIII was a fantastic little twist:

He knows that easy irony, that note of invincible good humour--a thousand death-knells could not disguise it.

(Also, I now have a sneaking love for the phrase 'potentially dodgy architecture'. Hee.)