Sketching from the window, here is Ben Jonson, part of the Barbican estate.
The people who live on the top floor of Ben Jonson have sunlit roof gardens. You can see one person enjoying his garden. He sits just at the bottom of the blue fire escape ladder.
There is also an interesting void space shown in the lower right of the picture. It was empty when I was drawing, but sometimes someone’s legs are visible, using the space for sunbathing. Sometimes they set up a table and chairs there.
Here is work in progress. I used colours: Mars Yellow, Burnt Umber, Prussian Blue and a bit of Perinine Orange.