"10. For a loss and expense claim under a construction contract to succeed, the contractor must aver and prove three matters: first, the existence of one or more events for which the employer is responsible; secondly, the existence of loss and expense suffered by the contractor; and, thirdly, a causal link between the event or events and the loss and expense. (The present case involves a works contract concluded between a management contractor and a works contractor; in such a case the management contractor is obviously in the position of the employer and the works contractor in the position of the contractor.) Normally individual causal links must be demonstrated between each of the events for which the employer is responsible and particular items of loss and expense. Frequently, however, the loss and expense results from delay and disruption caused by a number of different events, in such a way that it is impossible to separate out the consequences of each of those events. In that event, the events for which the employer is responsible may interact with one another in such a way as to produce a cumulative effect. If, however, the contractor is able to demonstrate that all of the events on which he relies are in law the responsibility of the employer, it is not necessary for him to demonstrate causal links between individual events and particular heads of loss. In such a case, because all of the causative events are matters for which the employer is responsible, any loss and expense that is caused by those events and no others must necessarily be the responsibility of the employer. That is in essence the nature of a global claim. A common example occurs when a contractor contends that delay and disruption have resulted from a combination of the late provision of drawings and information and design changes instructed on the employer's behalf; in such a case all of the matters relied on are the legal responsibility of the employer. Where, however, it appears that a significant cause of the delay and disruption has been a matter for which the employer is not responsible, a claim presented in this manner must necessarily fail. If, for example, the loss and expense has been caused in part by bad weather, for which neither party is responsible, or by inefficient working on the part of the contractor, which is his responsibility, such a claim must fail. In each case, of course, if the claim is to fail, the matter for which the employer is not responsible in law must play a significant part in the causation of the loss and expense. In some case it may be possible to separate out the effects of matters for which the employer is not responsible." (emphasis added)