What is material increase of risk test for ascertaining causation under English tort law?

The material increase of risk test is a legal test used in English tort law to determine whether a defendant’s conduct has caused the harm suffered by the claimant. The test is used to ascertain causation when the defendant’s conduct has created a risk of harm, but the claimant’s harm has been caused by some other factor. The test requires a court to consider whether the defendant’s conduct has materially increased the risk of harm, as opposed to merely creating a risk of harm that was already present. If the court finds that the defendant’s conduct has materially increased the risk of harm, then it may be held to have caused the harm suffered by the claimant.