Sentence:  Mother...considered that the exclusiveness of Peter's circle was <WSD>due</WSD> not to its distinction, but to the fact that it was an inner Babylon of prodigality and whoredom, from which every Kensingtonian held aloof, except on the conventional tip-and-run excursions in pursuit of shopping, tea and theatres. 
Meaning of the word marked with <WSD> tags:  Owing; ascribable, as to a cause.