You're right (it does taste terrible)- this from castlelager.co.za :
From barley to bottling, it takes a patient seven weeks in total to create a Castle Lager. The Castle brew is prepared for 18 days: 12 days of brewing and fermenting, and 6 days of maturation. The brew must go through a number of rigorous quality approval phases throughout the process before it may leave the brewery as Castle Lager.
By the way - if you ever see a Castle label you will notice that its won a gold medal (!) - from an agricultural show in 1907 (no, really)