http://bentasker.i2p/posts/blog/house-stuff/building-a-hard-pelmet-for-a-bay-window.html
The windows have a thick frame, which the curtain pole mounts have to reach out beyond, resulting in there being more than enough space for reflected light to work its way upwards and into the room. The effect in summer, is that at about 4am, any possibility of sleep is ended as a result of the room being flooded with sunlight. Things are a little better in Winter: the sun's assault starts later (if it even bothers to show up that day), but the room ultimately gets similarly illuminated.