asked the Prime Minister if he will list those topics on which it is not his practice to answer parliamentary Questions; and if he will list any changes in practice since 1972, indicating in each case the date on which the change was made and the relevant reference in the Official Report.

The matters on which I follow the practice of my predecessors in declining to answer Questions include security matters, telephone interception, Cabinet Committees and detailed arrangements for the conduct of Government business and lists of past and future engagements. I am not aware of any changes in practice since 1972. It is not possible to give a definitive and exhaustive list of Questions relating to my responsibilities which I might decline to answer on grounds other than cost, but, generally speaking, Questions that relate to the responsibilities of individual Ministers are transferred to them for answer.