Complex sentence: Under his tutelage in the 1920s, and that of Julius Beresford, Thames reached new heights, winning four events at Henley in both 1927 and 1928, something which no one club has replicated in the 20th century.
Split into simpler sentences: Under his tutelage in the 1920s, and that of Julius Beresford, Thames reached new heights. Under Beresford, Thames won four events at Henley in both 1927 and 1928, something which no club has replicated in the 20th century.