“115…There is a venerable principle of tax law to the general effect that there is a public interest in taxpayers paying the correct amount of tax, and it is one of the duties of the commissioners in exercise of their statutory functions to have regard to that public interest… For present purposes, however, it is enough to say that the principle still has at least some residual vitality in the context of section 50, and if the commissioners are to fulfil their statutory duty under that section they must in my judgment be free in principle to entertain legal arguments which played no part in reaching the conclusions set out in the closure notice. Subject always to the requirements of fairness and proper case management, such fresh arguments may be advanced by either side, or may be introduced by the commissioners on their own initiative.”