When Maniac returns to the McNab's house in Chapter 39, what is happening?

As Maniac walks into the McNab’s house, he sees a group bringing cinder blocks into the living room. McNab is creating a “pillbox”, a type of fortress, in his house. He’s also securing the windows with bars, creating a steel door, and barricading the house. When Maniac questions why they are doing this, George McNab states he is trying to prepare for an impending East Enders’ revolt.