Complex sentence: In the prototype these driving positions were directly in front of the superstructure; moving them forward improved visibility, but made communication very difficult-a problem as, in the Mark I, four men had to cooperate to steer the tank.
Split into simpler sentences: In the prototype these positions were directly in front of the superstructure; moving them forward improves visibility, but makes communication very difficult. This is an important drawback as, like in the Mark I, four men have to cooperate to steer the tank.