it's amazing how you come to understand everything AFTER the exams... *sobz*
Anyway, pre donoghue v stevenson times, one party did not owe another a duty of care unless their was a contract between the parties or if a previous case held that a duty of care existed in such a relationship
however, d v s held that as long as there was reasonable forseeability and proximity, a DOC can arise in virtually ANY relationship
then there comes a string of cases which rejects the proximity principle as a condition for the existance of a DOC and tries to come up with a universal test to see if a DOC existed and they all failed miserably (ok, some of them had some merits)
finally in perre v apand mchugh decided to give up looking for a universal test to apply to novel situations and instead devised an incremental approach, where a DOC exists if the relationship between plaintiff and defendant fits into a 'category' which courts previously decided that a DOC existed or if not, whether a logical 'incremental development' of an existing category would include the novel situation in question and whether such a development should be permitted, taking in consideration various factors.
If I remember correctly, the civil liability legislation reflects mchugh's approach i.e. we're back to pre d v s times