Sentence:  Mother...considered that the exclusiveness of Peter's circle was due 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 <WSD>conventional</WSD> tip-and-run excursions in pursuit of shopping, tea and theatres. 
Meaning of the word marked with <WSD> tags:  Ordinary, commonplace.