In this section:

Factthis is incorrect.

Damp proof courses, just like everything in nature, is subject to aging and degradation over time - a natural physical law. Why would damp proof courses be an exception and violate this universal law?

Let's look into this in a bit more detail. When someone examines the condition of the damp proof course, one usually just sees a thin 2-3 mm thin edge sticking out from under the building. For a 500 mm thick wall this is only about 0.5%, 99% of it being hidden "under" the wall. Let's be realistic here: how could anyone assess the condition of the DPC and say it's fine when 99% of it is invisible. It's like a doctor doing a diagnosis on a patient by looking at the tip of his tongue.

The video below presents some real examples of broken down slate damp proof courses.