The majority of building surveyors carry out surveys from ground level or with the use of a short ladder.  This will suffice for the majority of properties.  This particular property had one or two elements that could not be seen at all from ground level.

A very quick flight with a UAV, subject to a risk assessment, revealed the following:

A newly laid section of flat roof covering. Good!
What appears to be an asbestos cowl with a hole in it. Bad!