42 As the preceding discussion indicates, it is not a simple task to discern the objective purpose of rent review provisions in any particular case - or more generally. The difficulty lies in the fluctuations of the rental market and changing economic conditions. As a general proposition, the objective purpose of a rent review provision should be understood in the context of the rental market at the time the lease was executed, and by reference to the nature of the demised premises, and also, by reference to the length of the lease.[89] A safe starting point is to say that where a rent review provision is accompanied by a ratchet provision, the objective purpose is to benefit the landlord by ensuring an increase in rent, regardless of downward market trends. In the absence of a ratchet provision, it is uncontroversial to say that a variable rent, which might move upwards or downwards on review, is a method to maintain, so far as possible, the original bargain struck between the parties in real financial and current market terms. It is equally uncontroversial to say that, all things being equal, rents trend upwards over time - and more clearly so the longer the period of time considered. This, of course, must be qualified having regard to anomalous economic circumstances, such as a recession, depression, or property market crash. It must also be qualified where the demised premises is only capable of catering to a specific industry, which might be volatile, or liable to decline. However, in so far as rents normally increase over time, in my view, rent review provisions are normally to be regarded as being for the benefit of the landlord; their purpose being to safeguard the landlord against inflation and to maintain parity with the current rental market over time. This is especially so where the term of the lease is substantial. In my view, the purpose of clause 4.2 and Part B, read together, in the context of clause 4.1, clause 4.3 and Parts A and C of Annexure B, is to benefit the defendant by safeguarding it against the deleterious effects of inflation and to maintain parity with the current rental market over time. As indicated previously,[90] the consideration of the commercial purpose of a contractual provision is intrinsic to its construction.