“In performing [his function] an actuary must employ an expertise of great refinement which involves assessing the weight to be given to many and various contingencies and near imponderables. Some of these, such as mortality tables, may depend on statistical data and may be susceptible of more or less demonstrable validation. Others must necessarily be largely a matter of personal judgement. There is considerable scope for justifiable differences of approach and opinion among actuaries, and as the actuary’s function is essentially one of estimation, one actuary may very possibly reach a conclusion in a particular case which varies, perhaps widely, from the conclusion of another actuary on the same facts. The Court should be very slow to criticise or seek to control the exercise of any discretion or judgement reposed in or required of an expert of this kind in the exercise of a function of this character…