Having changed the appearance of Sir Alfred's home I had to change every panel in which its exterior appeard. Here's one from a bit later in the story - the early version is pretty bad, and looks even more of a fake location than the early first panel. What an improvement a bit of architecture and street life can make! (Okay, plus a gap of 6 years and a slight improvement in my drawing ability).
I have been asked before if I use Google Sketch-Up for buildings - no, definitely not! (I think you can tell that, actually, otherwise they'd probably be a lot more ambitious!) A ruler, a pencil, two or three vanishing points and a bit of patience (maybe a little impatience every now and then, too), and though it may take longer, I like the feeling that it's all my own work - warts and all. The photograph below shows a page I was working on last year with three sheets of paper attached, each holding a vanishing point, and the finished panel.