The original MkI model was superseded by the MkII model ( which had a symmetrical windscreen with an arched top ) in 1981 .
Production of the original MkI continued for Greater Manchester Transport and London Transport until 1983 and 1985 respectively .
The original MkI model was superseded by the MkII model ( which had a symmetrical windscreen with an arched top ) in 1981 , although production of the original MkI continued for Greater Manchester Transport and London Transport until 1983 and 1985 respectively .