“…the very use of the word 'judgment' makes it clear that the commissioners are required to exercise their powers in such a way that they make a value judgment on the material which is before them… Secondly, clearly there must be some material before the commissioners on which they can base their judgment. If there is no material at all it would be impossible to form a judgment as to what tax is due. Thirdly, it should be recognised, particularly bearing in mind the primary obligation, to which I have made reference, of the taxpayer to make a return himself, that the commissioners should not be required to do the work of the taxpayer in order to form a conclusion as to the amount of tax which, to the best of their judgment, is due. In the very nature of things frequently the relevant information will be readily available to the taxpayer, but it will be very difficult for the commissioners to obtain that information without carrying out exhaustive investigations. In my view, the use of the words 'best of their judgment' does not envisage the burden being placed on the commissioners of carrying out exhaustive investigations. What the words 'best of their judgment' envisage, in my view, is that the commissioners will fairly consider all material placed before them and, on that material, come to a decision which is one which is reasonable and not arbitrary as to the amount of tax which is due. As long as there is some material on which the commissioners can reasonably act then they are not required to carry out investigations which may or may not result in further material being placed before them.”