The entry point for this discussion into the second part is the question of what constitutes the tort of negligence. Negligence is a person failure to exercise the requisite standard of care which a reasonably prudent person would have been able to exercise if they were to find themselves in a similar situation.  Essentially, the tort of negligence involves a person failure to take adequate care for something for which they are responsible. 
This definition was reinforced in Blyth v Birmingham Waterworks Co  where negligence was defined as the omission by a defendant to do something which a reasonable man, who is guided by those considerations which ordinarily regulate the conduct of human affairs, would do, or it is the doing of something which a prudent and reasonable man would not do if they were faced with similar circumstances.
From this judicial definition, it is apparent that the tortuous liability for negligence could either be positive or negative. Positive liability arises where the tortfeasor acts in a manner inconsistent with how a reasonable person would have acted under similar circumstances. Negative liability for negligence arises in circumstances where it is the tortfeasor inaction which causes the claimant injury when such injury might not have occurred had the tortfeasor acted reasonably.
In a claim from negligence, the claimant has to prove the existence of three ingredients. The three constitute the elements of the tort for negligence.  First, the plaintiff must prove that the defendant owed them a legal duty of care.  Secondly, the claimant must show that the defendant breached the legal duty of care that was owed to them. Finally, the claimant has to show that they suffered some loss and/or injury as a result of the defendantâ€™s breach of the legal duty of care owing to the plaintiff. 
The test for a legal duty of care was spelt out by Lord Atkin in the case of Donoghue v Stevenson  as the neighbor test. The court affirmed that everyone always has to owe their neighbour a legal duty of care. However, the immediate question that springs to mind is that of who is one neighbour? The court defined a neighbour, from the legal standpoint, as any person who is so closely and directly affected by the defendant own acts in a way that requires that the defendant to reasonably have them in their contemplation as being so likely to be affected whenever the defendant is directing their mind to every particular act or omission. 
Given the foregoing test of the neighbour, what it therefore means is that one always has to take reasonable care in order to avoid acts or omissions which they would reasonably see as being likely to injure their neighbours. The neighbour test, therefore, brings into question the test of reasonable foreseeability for the injuries to the neighbour. Consequently, in order to establish whether a defendant owed the claimant a legal duty of care, the issue to be determined is that of whether the defendant act was reasonably foreseeable as was held in Tidy v Battman. 
In addition to foreseeability, another important factor for consideration is that of reasonableness. However, the question is what constitutes the standard of a reasonable conduct? This question was particularly dealt with judicially in Glasgow Corporation v Muir  where the court stated without equivocation that the standard of care for a reasonable man is an objective test.
Thus, to determine whether a defendantâ€™s conduct was reasonable or not, the question to ask is that of whether the defendantâ€™s act fell within the scope of that of a reasonable man. This is as opposed to the subjective question of whether the defendant did their best or not. The defendantâ€™s efforts have to be considered in the bigger picture of whether the average person would also have made similar efforts.
However, in the recent past, the court has been able to clarify on how to establish whether a legal duty of care exists. The test, developed by the House of Lords in the case of Caparo Industries v Dickman,  contemplates two possible alternatives under which a claimant could establish that the defendant owed them a duty of care. Under the first alternative, a claimant could prove a defendant owes them a duty of care if they demonstrate that there is earlier legal authority for a duty existing in the same circumstances.
However, under the second alternative, the court established a three step process through which the existence of a duty of care could be done. Under this alternative, the first question is to determine whether the loss or harm caused by the defendant was reasonably foreseeable. Secondly, the claimant must show that there was a sufficient relationship of proximity between the claimant and the defendant. Thirdly, the court must satisfy itself that the circumstances are such that it is fair, just and reasonable for the law to impose a duty of care on the defendant.
The standard of when a defendantâ€™s harm was reasonably foreseeable was judicially considered in Haley v London Electricity Board.  The brief facts were that the defendantâ€™s employees dug a trench in a pavement. The claimant, a blind user of the pavement, tripped up tools and fell into the trench whereupon the defendants denied liability for the injury. The defendants argued that the harm was not reasonably foreseeable because there were not so many blind users of the pavement.
It was however held that the defendants ought to have contemplated all the possible users of the pavement would have included even blind people. Because they failed to contemplate the blind users, they were therefore to be liable for the claimantâ€™s injury. The issue of foreseeability was also dealt with in Home Office v Dorset Yacht Co  where Borstal boys on trip to Brownsea Island escaped and damaged the claimantâ€™s yacht. The Home Office owed a duty of care to the claimant as the officers should have been in charge of the prisoners. To the court, it should have been reasonably foreseeable that Borstal boys are likely to play mischief when those in charge failed to take care of them.
How about the question of proximity? In the everyday sense proximity means the physical closeness.  However, in the legal sense and for the purposes of the three stage test, proximity will be satisfied if the product causes the injury to the claimant. Besides, proximity may also be established by the relationship between the defendant and the claimant. Such relationship could also encompass circumstances where the defendant has a degree of control over the situation which he could have used to prevent the danger from occurring, i.e. the time can be a factor.
Therefore, if there is a long time lapse between the time when the harmful product left the defendant control, and the time when the injury actually occurs, then proximity may be considered to have been absent. This was especially reiterated in Evans v Triplex Safety Glass.  The claimant bought a car fitted with a toughened glass windscreen from the defendant. He was injured when the glass shattered while he was driving and sued the defendant for the injury. It was however held that the defendant was not liable for the injury because the proximity between them had been obliterated with the lapse of time.
Once the claimant establishes the existence of the first two conditions, the court is then obliged to inquire into whether it would, under the circumstances, be fair, just and reasonable that the law should impose a duty of care on the defendant. To establish whether it would be fair, just and reasonable to impose a duty of care on the defendant, the court must exclude the possible presence of a number of factors which would make it inequitable on the defendant to have a duty of care.
There are three situations which may cause the courts to reject the claim of a duty of care on the basis it is not fair just or reasonable. These are, firstly, where the existence of a duty of care would open the floodgates to many claims of the same nature. Secondly, where the circumstances are such that the claimant is considered to have been the author of his own misfortune, the court would not impose a duty of care on the defendant. Thirdly, where the defendant is a public authority exercising a public function. 
These considerations were eruditely captured in the judicial decision of Hill v Chief Constable of West Yorkshire.  The mother of the last victim of a deranged man, Peter Sutcliffe, sued the police in negligence for having failed to catch Sutcliffe earlier. The House of Lords dismissed the claims on the basis that the police did not owe her a legal duty of care. In the courtâ€™s view, the police do not generally owe individuals a duty of care because if they were to do so, then that would compromise their function. In the circumstances, it would not have been fair, just and reasonable for the police to owe a duty of care to the individuals.
Considering the Caparo test, the question that remains is what is the extent to which the concept of duty of care in negligence has developed so that it ensures that both the claimant and defendant are treated fairly? In other words, what improvements did Caparo make to the neighbor test of Donoghue? It is to be recalled that the neighbor test only required that the defendant ought to have been reasonably foreseeable. Consequently, a defendant who act or omission caused a claimantâ€™s injury was liable for the injury.
From the foregoing, the neighbor test was quite restrictive and placed a lot of obligation on the defendant. The flipside was therefore that the standard was quite liberal for claimants who could easily prove their case. However, Caparoâ€™s test comes in to temper this leeway. This is because the second and third conditions are basically aimed to ensure that the courts do not unduly burden defendants with duties when it would be entirely unjustifiable.
Unjustifiable grounds include the three circumstances already highlighted. Essentially, Caparoâ€™s three tier test attempts to balance the interests of the claimant vis-Ã -vis those of the defendant. It is no longer just a question of the claimantâ€™s interests being of concern to the court. The court has now had to incorporate the interests of the defendant as well. The balancing of the partiesâ€™ interests is therefore the extent to which the concept of duty of care in negligence has developed so that it ensures that both the claimant and defendant are treated fairly.