The idea for this sketch actually came from a sketch by Richard Briggs that appeared in Stephanie Bower's new book 101 Sketching Tips. It's just a simple 2-colour pen and ink sketch that appeared on page 16.
I was just trying to draw with the same style. It's a technique that allows you to work really quick as the focus is on lines.
The pen I used was the Hero 501-1 fountain pen that has a fude nib. This pen I had has ink flow issues so I'm using it as a dip pen now. Anyway, you should not load India inks inside a fountain pen. India ink will clog anything. See that blue coat of ink on the nib. That's dried ink that can't even be washed off with water. I had to scrap the dry ink off in order to clean the nib. Imagine this ink inside a fountain pen. How are you going to clean the insides when the ink dries?
Initially, I just had the people on the streets but the sketch looks off-balance because blacks on top and blues at the bottom. So I added more people onto the buildings. Since I'm using blue ink to draw people on the streets, those who look at this sketch will be able to make the association or recognise the pattern that those blue dots and squiggly lines on the buildings are actually people too.