I read Joanna Cherry's recent Agenda article on the legal issues surrounding Scotland's continued membership of the EU with interest.

It makes no allowance for the fact that Scottish independence would not be welcome to all other member states, for a variety of reasons.

The Spanish Government has already made its position clear. I have no doubt that an independent Scotland could in due course become a member state of the EU. But it would not happen within the timescale, or on the terms, asserted by the Yes campaign.

We need to think through the process. If we were to vote to leave the UK, we - and they - would have a lot to arrange before actual independence.

We have been building up joint institutions for 300 years. It would take more than 18 months to set up sensible alternative arrangements - particularly with a UK General Election in the middle of the process.

Once a deal was done, we would need legislation at Holyrood and Westminster, and probably a treaty, which would need to be ratified by both states.

The substance of our approach to the EU would depend, in many areas, on what we had agreed with the UK. The arrangement - whatever it might be - on a currency would be only one example.

The Article 48 process favoured by the White Paper was simply not designed to short-circuit the process for joining the EU. Any Member State could effectively block its use. Nor would it be sensible from our point of view.

We would not have a seat at the table. (The UK would have to look to the interests of its own people post-independence.) And the process would not be quick.

That is why I take the view that the correct legal basis for an approach to the EU is Article 49, which sets out the process by which European states can apply to join.

More to the point, other member states - and the EU institutions - are likely to take that view too. The Article 49 process enables them to satisfy themselves that the applicant state is able and willing to fulfil its obligations.

Since, according to the White Paper, we would be asking for the same special terms that the UK currently enjoys, that process would be particularly important for other member states, who are unlikely to agree to everything we would want. It too would take time.

Joanna Cherry quotes one or two cases in which the European Court of Justice has emphasised the importance of the institution of EU citizenship.

And others seem to think that EU citizenship is some sort of mystical status, so that Scots would continue in some (unspecified) way to be European citizens after independence.

For the EU, citizenship is certainly important. But there is no magic about it. Article 50 of the treaty already provides for a member state to leave the EU. When it does, its citizens will no longer be EU citizens. We are EU citizens because we are nationals of the UK. If we vote to leave the UK, we are voting to stop being EU citizens.

We cannot pick and choose among the consequences of a decision to leave the UK. Independence would mean that Scotland would not be in the European Union (or the UN, or the Council of Europe, or Nato).

That is a natural, inescapable result of what we would have voted for - the freedom to make our own decisions as to which of those bodies or organisations we would seek to join.

To sum up, it would take more than 18 months to reach a (sensible) deal with the UK on the terms of independence - and longer than that to pass the necessary legislation. We could not (sensibly) approach the EU until after we had done all that. So there would be no advantage - and a lot of drawbacks - in trying to use Article 48. Article 49 is the only article that would enable us to negotiate our membership ourselves.