The law limits the extent of the defendant's obligation. A defendant is only obliged to take reasonable steps to prevent foreseeable harm, and only if the risk of harm was 'not insignificant'.
Even if a defendant owes a duty of care to a plaintiff, they are not obliged to prevent harm that is unforeseeable. Nor is a defendant required to take more than reasonable steps to prevent harm, even if it is foreseeable. That would impose too large and unfair a burden on the defendant.
These matters, though developed by the courts, are now governed by legislation.
The extent to which the harm must be foreseeable, and what steps should reasonably be taken in particular circumstances to prevent the harm, are important questions which we will deal with.