Strict liability offences require no proof of mens rea for some or all of the actus reus. D must have committed the actus reus voluntarily, but D does not have to be at fault. In ALPHACELL LTD v WOODWARD the pumps a company had installed broke down and caused pollution to flow into a nearby river. There was no evidence that the company had been negligent (at fault), but they were strictly liable because it was of the utmost public importance that rivers should not be polluted.