Complex sentence: Watney Mann ale and stout brewing ended on 26 May 1974, and most of the original brewery was demolished, only the relatively modern office block was retained as part of Carlsberg's brewery, renamed Jacobsen House.
Split into simpler sentences: Watney Mann ale and stout brewing ended on 26 May 1974, and most of the original brewery was demolished. Above ground the relatively modern office block was retained as part of Carlsberg's brewery, renamed Jacobsen House.