Robert,
I flew over London yesterday too. I felt like the flying nun! LOL
My roof has always been gray, still is, but I guess it is the sun that gives it sort of a red glow. The street to the right of mine is a block that has red roof tiles. The population density is quite high indeed.
Jon,
Wonderful pictures!! Lincoln looks beautiful from the air. Lincoln cathedral looks a bit like Westminster Abbey, doesn't it?