asked the Prime Minister how far it is still the opinion of his scientific advisers that, given the equipment and facilities envisaged when the conference on the suspension of nuclear test explosions reached agreement on this point last December, nuclear test explosions can be detected.

Since the technical experts met last summer, certain new information has become available which, in the view of Her Majesty's Government and the United States Government, throws doubt on the effectiveness of the proposed control system to detect underground explosions of low yield. The information has been communicated to the Russian representatives at the Geneva Conference with the suggestion that it should be studied by experts from the three participating countries.

Are we to understand, therefore, from the Prime Minister's reply that the agreement already reached at Geneva about the detectability of tests and the machinery that would be required is now to be reopened and the conference at Geneva is set back in its consideration of this matter?

I do not think this need affect the political terms of the agreement. It is a matter which the scientific experts will have to take into account.