It is said that the form of the sub-section places the burden of disproof on the defendant. For the requirement of prompt notice after the injured party becomes aware of the impossibility of identifying the car inflicting the injuries is expressed in the form of a proviso. "There is a technical distinction between a proviso and an exception, which is well understood. All the cases say, that if there be an exception in the enacting clause, it must be negatived: but if there be a separate proviso, it need not" - per Abbott J. in Steel v Smith [1] . The distinction has perhaps come to be applied in a less technical manner, and now depends not so much upon form as upon substantial considerations. In the end, of course, it is a matter of the intention that ought, in the case of a particular enactment, to be ascribed to the legislature and therefore the manner in which the legislature has expressed its will must remain of importance. But whether the form is that of a proviso or of an exception, the intrinsic character of the provision that the proviso makes and its real effect cannot be put out of consideration in determining where the burden of proof lies. When an enactment is stating the grounds of some liability that it is imposing or the conditions giving rise to some right that it is creating, it is possible that in defining the elements forming the title to the right or the basis of the liability the provision may rely upon qualifications exceptions or provisos and it may employ negative as well as positive expressions. Yet it may be sufficiently clear that the whole amounts to a statement of the complete factual situation which must be found to exist before anybody obtains a right or incurs a liability under the provision. In other words it may embody the principle which the legislature seeks to apply generally. On the other hand it may be the purpose of the enactment to lay down some principle of liability which it means to apply generally and then to provide for some special grounds of excuse, justification or exculpation depending upon new or additional facts. In the same way where conditions of general application giving rise to a right are laid down, additional facts of a special nature may be made a ground for defeating or excluding the right. For such a purpose the use of a proviso is natural. But in whatever form the enactment is cast, if it expresses an exculpation, justification, excuse, ground of defeasance or exclusion which assumes the existence of the general or primary grounds from which the liability or right arises but denies the right or liability in a particular case by reason of additional or special facts, then it is evident that such an enactment supplies considerations of substance for placing the burden of proof on the party seeking to rely upon the additional or special matter: see Morgan v Babcock & Wilcox Ltd. [1] ; Pye v Metropolitan Coal Co. Ltd. [2] ; Darling Island Stevedoring & Lighterage Co. Ltd. v Jacobsen [3] ; Barritt v Baker [4] ; Dowling v Bowie [5] .