If you look behind the arches on Ruston Quays, you can see that what we have is some fairly thin plastic parts hiding a wooden substructure. It's how we tend to build model railways, a facade hiding the ugly truth.
Not very realistic?
Well have a look at this picture of work taking place around London Bridge station shared on Twitter by Tim Dunn. Those are basically full-sized Wills plastic kits they are putting up aren't they?