Sami was a knowledgeable intelligent man obviously, so I can't see him wanting to create a root barrier where there were no trees, or the trees had already been felled and stump ground. My own opininion is that the two areas of concrete (what looks like a dry mix of cement and all-in-one aggregate from the part-used bag at the house front) are simply shallow bases for flags or block paving, rather than deep root barriers. Both are located under windows and would form a hard surface to stand on instead of grass for anyone cleaning them.
It would seem odd for Sami to install paving to clean some windows and not others, so this theory doesn't quite work. Otherwise, we think you're right here. We realised that the plans only mark trees which were subject to a preservation order. There are trees and conifers which aren't subject to such an order and which therefore don't appear on the plans.
Sami has marked "five new trees" which were "introduced on the site since 1986" A through to E.
These trees were felled: T4 (Ash), 6 (Lime), 5 (Lime)
Of the new trees Sami planted himself, he subsequently removed B and E.
Mark only recalls being present and witnessing the work conducted on the site at the front of the house. He is confident that this was a root-barrier. We could dig exploratory trenches / use ground survey equipment next to both sites to confirm the depths, and test our assumptions, but this probably wouldn't have significant enough bearing on the case to justify disturbing the current owners or indeed the cost of such work.