Ministry of Defence v AB and Others [2010] EWCA Civ 1317

Court of Appeal 
Facts: In 1952, the British Government conducted nuclear and fusion bomb tests in the Pacific, exposing the claimants (C) to radioactive fallout. The exposure varied in time, location, and duration among the claimants. A study indicated that the claimants had more chromosomal aberrations than normal, suggesting exposure to ionizing radiation, but no direct link was established between this exposure and the diseases suffered by the claimants. 

Held : The claimants could not rely on the Bonnington principle for cancer, as it is an indivisible condition. Exposure to a harmful agent does not worsen cancer but rather either causes it or does not. The Fairchild exception could not apply as the causes of the claimants' conditions were not known, and radiation was only one of several possible causes. The court was not willing to extend the Fairchild exception beyond its narrow scope. 

• Smith LJ : Causation in tort generally requires evidence that, but for the tort, the claimant would not have suffered the injury. Challenges arise when there is more than one potential cause of the condition, with only one attributable to the defendant’s negligence. In this case, the claimants’ conditions had several potential causes, including but not limited to radiation.