The emphasis on speed unbalanced the British designs; on limited engine power, the speed was possible only by sacrificing armour protection (by comparison infantry tanks operating at soldiers' pace could carry far more armour). The idea that "speed is armour" was considered most important in the Royal Tank Corps. It was not realised that the principle of mobility was a liability against the German policy of accepting lower speeds for superior armour and armament, ensuring that even one round from a German medium tank could easily destroy a cruiser.