Bonnington Castings Ltd v Wardlaw

Bonnington Castings Ltd v Wardlaw [1956] AC 613 is an English tort law case, concerning causation, and material contribution to harm.^[1]

Mr Wardlaw worked in Bonnington's workshop for 8 years where there was a pneumatic hammer creating silicone dust that he inhaled. He then got pneumoconiosis. Bonnington was not liable for the hammer dust at the time because there was no way to prevent it. But Bonnington could prevent the dust, it was determined, from swing grinders by putting in an extraction fan.

The House of Lords held that Bonnington had to compensate Mr Wardlaw for materially contributing to his injury. Lord Reid held that a statutory duty does not change the standard of proof from the balance of probabilities. De minimus non curat lex is the principle that small contributions are not actionable, but anything above is a ‘material contribution’. Dust from the grinders ‘made a substantial contribution’ even though more dust came from the hammers.

• English tort law