EXTRA INFO I “THINK” MIGHT HELP
So in regards to liability/ breach of duty
Bolton V stone 1951 – calculus of risk – has breach of duty occurred?
Miss Stone was injured when she was struck by a cricket ball outside her home. She brought an action against the cricket club in nuisance and negligence. The cricket field was surrounded by a 7 foot fence. The pitch was sunk ten feet below ground so the fence was 17 feet above the cricket pitch. The distance from the striker to the fence was about 78 yards and just under 100 yards from where the claimant was standing. A witness who lived in the same road as the claimant but close to pitch said that five or six times during the last 30 years he had known balls hit his house or come into the yard. Two members of the Club, of over 30 years’ standing, agreed that the hit was altogether exceptional to anything previously seen on that ground.
Held, that the members of the club were not liable in damages to the injured person, whether on the ground of negligence or nuisance.
Although the possibility of the ball being hit on to the highway might reasonably have been foreseen, this was not sufficient to establish negligence, since the risk of injury to anyone in such a place was so remote that a reasonable person would not have anticipated it.
In regards to the “rubber stopper” how it was not unsafe. It was a “new system” meaning it made to work anyway. Reasonable precautions were taken
Latimer v AEC  AC 643 House of Lords
The claimant worked in the defendant’s factory and slipped up on the factory floor. The factory had become flooded due to adverse weather conditions. The defendant’s had put up warning signs mopped up and placed sawdust in the most used places to make it as safe as possible. The trial judge held that there had been a breach of duty as the defendants should have closed the factory if it was unnsafe. However, no argument had been advanced on this.
There was no breach of duty. There was no duty to close the factory. The defendant only had to take reasonable precautions to minimise the risk which they had done. There was no need to go to great expense to eliminate any possible risk and thus no obligation to close the factory.
Okay, this could argue the Current state of knowledge.
Although he was not instructed to use the new system, it was not know it would fail.
Roe v Minister of Health  2 WLR 915 Court of Appeal –
Two claimants had been given an anaesthetic for minor operations. The anaesthetic had been contaminated with a sterilising fluid. This resulted in both claimants becoming permanently paralysed. The anaesthetic had become contaminated during storage. The anaesthetic was stored in glass ampoules which were emerged in the sterilising fluid. It transpired the ampoules had minute cracks which were not detectable with human eye. At the time it was not known that the anaesthetic could be contaminated in this way and the hospital followed a normal procedure in storing them this way.
There was no breach of duty. The risk was not foreseeable as it was an unknown risk at the time.