Sir Peter Marshall was Commonwealth Deputy Secretary-General 1983-88 and UK Permanent Representative to the UN in Geneva 1979-83.  He is a former Chairman of the Royal Commonwealth Society.

The first Permanent Under-Secretary at the Foreign Office under whom I had the pleasure of working was Sir William (later Lord) Strang, a doughty Scots scholar-administrator. He was forbearing in his treatment of the juniors. On one occasion, when I had favoured him with some of my best ideas, he inquired: “and how would you propose to translate that into administrative fact?” I have treasured this conversation-stopper ever since. For me, it is “the Strang Test”. I find it indispensable in the present Brexit context.

Withdrawal from the EU would involve an administrative effort of epic proportions. We would need to address more or less simultaneously at least the following “First Eleven” of questions, or groups of questions. The batting order takes account of the administrative priority they might demand:

(1) Structure and process for effective management of the whole withdrawal exercise;

 (2) Establishing a satisfactory trading arrangement with the EU/Single Market;

 (3) Shaping of our general relationship with Europe, including the possibility that the EU entirely unravels;

(4) Promoting our general economic prospects;

 (5) Ensuring our overall international financial viability;

 (6) Preserving the integrity and unity of the United Kingdom;

 (7) Maintaining our full participation in world wide political, economic and social co-operation, especially on development and “global” issues;

 (8) Safeguarding our national security in all its different aspects;

 (9) Preserving and enhancing our international standing/“soft power”;

 (10) Regaining national sovereignty, especially in law-making and control of our borders;

 (11) Managing immigration in all its ramifications at home as well as abroad.

Where can we find Vote Leave addressing the epic administrative effort that will be needed to pass the Strang Test?

There is total uncertainty about the structure and process of the withdrawal exercise. There is a multitude of answers to what the trading arrangements with the EU will be. There is an irresponsible indifference to the future of the EU which is not shared by any of our principal partners. And it is on successfully addressing these first three points that the whole exercise depends.

All of this does not disturb the serenity of Michael Gove. In a recent speech, he declared that, after leaving, any difficulties we encountered over reaching a trading agreement would be quickly settled by “our highly skilled Foreign Office civil servants”. Where would these paragons have been beforehand?

And it scarcely need be added that the testimony of those few of us who have experience of operating on the outside – while de Gaulle was keeping us out of the EEC – and thus have a personal idea of what we stand to lose by withdrawal, are held to be of no account.

The failure to address the first three points makes success even less likely on the subsequent points.

Promoting our general economic prospects. Vote Leave claims that Brexit would “unleash” in us untold creative energies currently “shackled” by Brussels regulation and red-tape. But the inadequacies of our present economic performance, such as poor productivity and a distorted housing market, are the product of long-standing defects which need urgent attention regardless of the outcome of the referendum.

Ensuring our international financial viability. We have run a current account deficit for each and every one of the last 30 years. To date this highly vulnerable situation seems to have been contemplated with perfect equanimity by all concerned. The total of financial inflows from overseas required to meet it may be small, compared with our borrowing overall. But surely this is a case of “letting sleeping anomalies lie”. If suddenly awoken, e.g, by Brexit, the anomalies could do us great mischief.

Preserving the integrity of the United Kingdom. Vote Leave told the Foreign Affairs Committee that they “consider it highly unlikely that any part of the UK would decide to leave the UK in order to join the unreformed EU”. Even if the Union survived, it could be seriously dysfunctional.

Safeguarding our national security. Vote Leave emphasises that NATO, not the EU, is the key to our security. This is far too simple an approach to an immensely complicated problem. To suggest, however, following the much publicised observations of Sir Richard Dearlove, that leaving would make Britain more secure is to apply a questionable sectoral judgment to the situation as a whole – an example the traditional and all too common Fallacy of Composition.

Regaining national sovereignty.The notion of sovereignty has been of much service as a Brexit rallying call. It reaches its emotive height in the claim made in general terms that “European Law overrides British law”: i.e: the rulings of the European Court of Justice take precedence over the law of member countries in matters in which it has been given competence by the member states. This is not a form of tyranny imposed on us alone. It is a logical but somewhat exotic derivative from a long established international principle in treaty-making, designed to ensure that all member states adhere to the obligations in which they agree to enter. If you involve yourself internationally, you cannot be wholly sovereign. Only hermits achieve that particular state of bliss.

Managing immigration. The idea that “control of our borders”, supposedly obtainable by withdrawal from the EU, will deal with the matter is fanciful. The problem is far deeper, wider and more long term than Vote Leave assumes. And there is no hope of a solution without extensive international consultation and co-operation – it is inherently not something we can tackle alone.

This is the first of five columns that this site will publish during the run-up to June 23rd.