Complex sentence: Heyer stresses the crucial importance of gaining admission to the club: despite the fact that the actual entertainment was notoriously dull and the refreshments inferior, exclusion from Almack's was the ultimate social failure.
Split into simpler sentences: Heyer stresses the crucial importance of gaining admission to the club. Despite the fact that the actual entertainment was notoriously dull and the refreshments inferior, exclusion from Almack's was the ultimate social failure.