"I am persuaded that the modern case law recognises a legal duty owed by the revenue to the general body of the taxpayers to treat taxpayers fairly; to use their discretionary powers so that, subject to the requirements of good management, discrimination between one group of taxpayers and another does not arise; to ensure that there are no favourites and no sacrificial victims. The duty has to be considered as one of several arising within the complex comprised in the care and management of a tax, every part of which it is their duty, if they can, to collect."