The hon. Lady will perhaps read in Hansard that her right hon. Friend mentioned that. The only point I make is that presumably that might be examined. The question is not whether that happens, but whether we have any control over it. That is the key point.

From the four points that I have outlined it will be seen that the Government attach great weight to the arms control implications of strategic research and possible deployments on both sides. Whatever the eventual outcome of such research, it is clear that, for the foreseeable future, Western security will depend upon the maintenance of nuclear deterrent forces. The immediate task, therefore, is to try to get reductions in the levels of these forces while maintaining strategic stability. That is the Western aim at the negotiations in Geneva.

The Soviet Union, however, continues to seek to hold agreement in this central area of strategic reductions hostage to a ban on the SDI, or a ban on space strike arms, as it terms it. The Soviet Union has mounted a major campaign to try to cast doubt on the motivation behind the SDI, notwithstanding its own research activities in related fields, and to foster alarm in the West about the consequences of pursuing it. We have seen these scare tactics before, over cruise missiles prior to their deployment in 1983. We have seen the benefits which a firm response can bring. We will continue to take a more balanced view, and will encourage the Soviet Union to do the same. Research work on ballistic missile defence will continue on both sides as it has since the 1960s. Nothing that we say today will alter that. There is no reason why this work has to be a stumbling block to arms control agreements if both sides do not wish it to be so. The United States has made it clear that the SDI research programme will be conducted in full conformity with the provisions of the anti-ballistic missile treaty. The United States has also made it clear that if SDI research yields positive results it would, after consulting the allies, consult and negotiate with the Soviet Union, in accordance with the terms of the ABM treaty, on how deterrence could be enhanced through a greater reliance by both sides on defensive systems.

If the Soviet Government want more certainty before committing themselves to arms reductions, they should take up the United States' invitation to discuss in the Geneva negotiations the relationship of offensive and defensive systems. In this way, each side could establish sufficient confidence in each other's intentions and in the framework of their security relationship to enable mutual reductions to be made in their massive strategic arsenals. The right way forward is through such discussions, but so far the Soviet Government have refused to go down this path.

It is within the framework of the four points, including our clear commitment to strategic stability and to arms control, that the British Government have viewed the question of participation in SDI research. As I have pointed out, this research, on both sides, covers technologies of relevance not just to ballistic missile defence. It embraces technologies which will be widely applicable in the battlefield of the future. Neither the British Government, nor our high technology companies, could afford to stand apart from such research. Nor have they done so. Within our defence research establishments and within other research institutions outside the Government, work has been under way in areas relevant to the SDI because these are areas relevant to our own defence effort and to the civil economy in the future.

We could have chosen as a Government to stand aside altogether from the SDI. Had we done so, we would have forgone the opportunity of an information exchange with the United States of immense potential benefit to our future defence programme. We could have abandoned the approach of Anglo-American defence co-operation which, under successive Governments, has served us so well. We could not, of course, have prevented British companies or universities from participating in the SDI if they had wished to do so, but they would inevitably have had to do so solely on United States' terms.

Instead, we have chosen the path of regulating and formalising our participation in a way which will provide a substantial opportunity for British companies and institutions to compete on equal terms with their United States counterparts. This was the approach enshrined in the memorandum of understanding signed by my predecessor, my right hon. Friend the Member for Henley (Mr. Heseltine), and Mr. Caspar Weinberger in December. This memorandum and the detailed agreements under it set out procedures for the participation of British institutions in United States funded work in a way which enables them also to use the fruits of this work for our benefit. It also facilitates a wider information exchange. Of course — and properly — it provides arrangements to safeguard security on both sides where this is necessary. It would be quite wrong and wholly unrealistic to proceed otherwise.

The United States Administration have emphasised their wish that there should be substantial British participation in United States-funded work. While they can provide no guarantees of the scale of our participation, their commitment is clear. What is now needed is a response for British companies, with the help of the British Government, fully to exploit this opportunity. We for our part have established within the Government an office to support SDI participation. We are anxious to work in partnership with industry and I am delighted that a presentation this week on opportunities for participation was over-subscribed twofold. It is early days in the programme, but some contracts have already been placed, including two in optical computing. Discussions are well advanced on a wide range of further opportunities for early British participation in the programme.

I maintain that the Government's approach is firmly based on the reality of the present situation—the reality of the need to take account of Soviet actions as well as of Soviet public statements and the reality of the need to take account of technologies which are not only of potential relevance to our future conventional defence effort but open up new possibilities, no more than that, for the relationship between strategic offence and defence in the long term. It is right that we should address those realities properly and fully, and it is right that we should ensure that this country has a research base capable of underpinning both its defence effort and the civil economy of the future.

It is inevitable, I suppose, that the Opposition should have sought to tackle these issues by focusing in a one-sided and anti-American way on the strategic defence initiative. If we were to follow their path, we should isolate ourselves from reality and weaken our capacity to work towards a safer and more secure world for all—both in the East and in the West. For those reasons, I urge the House most strongly to support the Government's amendment.