‘’…what a reasonable person having all the background knowledge which would have been available to the parties would have understood them to be using the language in the contract to mean’’, …And it does so by focusing on the meaning of the relevant words…in their documentary, factual and commercial context. That meaning has to be assessed in the light of (i) the natural and ordinary meaning of the clause, (ii) any other relevant provisions of the lease, (iii) the overall purpose of the clause and the lease, (iv) the facts and circumstances known or assumed by the parties at the time that the document was executed, and (v) commercial common sense, but (vi) disregarding subjective evidence of any party’s intentions.’’