"My Lords, I accept, as both counsel agree, that in a case where there is an issue involving a public authority as to a question of public law, your Lordships have a discretion to hear the appeal, even if by the time the appeal reaches the House there is no longer a lis to be decided which will directly affect the rights and obligations of the parties inter se. The decisions in the Sun Life case and Ainsbury v Millington (and the reference to the latter in Rule 42 of the Practice Directions Applicable to Civil Appeals (January 1996) of your Lordships' House) must be read accordingly as limited to disputes concerning private law rights between the parties to the case. "