"That for which a plaintiff is to be compensated in this regard is the loss of a capacity; that, at the beginning and the end, is the loss for which compensation is to be assessed. However, there are several ways in which, according to the facts, the assessment of that compensation may be approached. It may be approached simply by fixing the sum seen to be appropriate to that loss as such. The difficulties involved in the fixing of that sum - and in verbalizing the principles upon which it is to be achieved - need not be canvassed. But frequently (and this was the point to which the observations in the cases referred to in Allan v Loadsman were directed) the plaintiff, or the defendant, seeks to quantify the compensation for loss of that capacity by attempting to establish what the weekly wage loss is which will be suffered because of the loss of that capacity, and by arriving at a sum by applying the conventional tables to this, with appropriate discounts. This may be a perfectly permissible way of quantifying the loss in a particular case. It is often used, no doubt because it is felt that it will provide a greater sum than the alternative approaches. In some cases, the weekly wage loss quantification, and the sum derived from it, will alone be accepted as sufficient compensation; in other cases it may be necessary to add an additional sum by reference to such other aspects of the loss of the capacity as may not be fully compensated for by the mere weekly wage loss so dealt with."