This is one of the first cases is tudied when i was studying law hope it helps.
Donoghue v Stevenson  the founding case of tort law.
Claimant had gone to a cafe with a friend, who had bought her a drink of ginger beer. She had poured some of the drink into a glass and consumed it. When she poured the rest she found the decomposing remains of a dead snail.
Claimant became unwell and brought a claim of tort negligence against the manufacturer.
Because this was a unique case it was decided to first establish if it was legally possible for the manufacturer to be liable in law. This meant that the House of Lords considered only the issue of legal liability (the H of L referred the issue of factual liability back to the court, in which the case was started, so they can determine the facts within the case - e.g. was there a snail within the bottle and whether the manufacturer was negligent etc).
However, the House of Lords did decide that the manufacturer could be liable in certain circumstances. In deciding the legal principles, Lord Atkin commented:
"The rule that you are to love your neighbour becomes in law, you must not injure your neighbour: and the lawyers question, Who is my neighbour? receives a restricted reply. You must take reasonable care to avoid acts or omissions which you can reasonably foresee would be likely to injure your neighbour. Who then is my neighbour? The answer seems to be - persons who are so directly affected by my act that I ought reasonably to have them in contemplation as being affected when I am directing my mind to the acts or omissions which are called in question."