AN independent Scotland may be blocked from joining the European Union if it insists on removing Trident before the UK finds an alternative base for the nuclear missile system, according to one of the world's leading defence experts.

Professor Malcolm Chalmers, deputy director general of the defence and security think tank the Royal United Services Institute in London, gives the assessment in an article to be published later this week in The Herald as part of the latest instalment of our Scotland's Future series.

His intervention comes a week after First Minister Nicola Sturgeon unveiled her route map to a second independence referendum with a proposal to hold a new vote on 19 October 2023, should the Supreme Court rule that her government's legislation to do so using Holyrood powers is lawful.

She has referred the legislation to the judges after Prime Minister Boris Johnson has repeatedly refused to agree to a new referendum under the process which preceded the 2014 referendum. 

Should the court rule the legislation is not within Holyrood's powers, the First Minister said the SNP will campaign at the next general election on the single issue of "Should Scotland be an independent country?" and regard the poll as a "de facto" referendum on independence.

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Professor Chalmers explains that if the new state demands the swift removal of Trident it would find its plan to join the EU put in jeopardy as most of of the bloc's 27 members are members of Nato's planning group.

He says EU members of Nato's planning group would resist Scotland's EU application as the UK would be effectively put in a position of having to give up its nuclear weapons. Nato membership would also be unlikely in these circumstances, he argues.

“If Scotland were to insist on Trident’s removal from Faslane before the UK could relocate to another operating base safely, its chances of joining either Nato or the EU would be slim. 

"The UK would find it very hard to maintain an operational nuclear deterrent. As one of its first acts as an independent state, Scotland would have decided that one of its immediate priorities was the disarmament of the UK against the latter’s wishes," he writes.

"If Scotland were nevertheless to insist on rapid removal, most Nato members would view a membership application with considerable suspicion. This reluctance would likely spill over into the EU, most of whose members participate fully in Nato’s nuclear planning group.”

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However, he goes on to add that if Scotland were to accept a longer timetable to remove Trident it would have considerable bargaining power.

"If Scotland were provisionally prepared to accept longer-term (though not indefinite) Trident basing, it would have an immensely strong bargaining card," he writes.

"By making the UK dependent on its goodwill for retaining its nuclear deterrent, Scotland could marginalise those – of whom there could be many after a Leave vote - who would be tempted by the prospect of taking a more punitive approach."

He adds: "If Scotland wanted to be a ‘normal’ European state, it would therefore have to accept the full nuclear implications of what Nato membership means.

"If it were to do so, and was supported by the UK, it would likely be welcomed with open arms. If, instead, Scotland insisted on the immediate expulsion of Trident, it would likely be seen as yet another problem for European security, rather than part of the collective effort to address those problems."  

The SNP's current policy, passed overwhelming at the party's conference last September, is for Trident to be removed from Scotland in the first three years after an independent Scotland is set up or within five years of a Yes vote, taking account of a two year period to establish the new state.

Professor Chalmers estimates it could take the UK Government more than a decade to find an alternative base to Faslane for Trident.

His assessment presents a major dilemma the SNP will face in the forthcoming independence campaign.

The party is strongly in favour of an independent Scotland joining the EU and has underlined the country's opposition to Brexit - 62 per cent of Scots voted to remain - as a key justification for having a second independence referendum.  It also strongly backs Nato membership. However, it also favours the swift removal of Trident from Scotland.

The First Minister may have to persuade her party to accept a longer timetable of removing Trident if she wants an independent Scotland to become both a member of Nato and of the EU.

A number of experts in the latest Scotland's Future series raise possible compromises that may be open to the SNP including whether the Faslane naval base could be leased out to the UK's Ministry of Defence for a base for Trident until it found an alternative site in the UK.

The move which could provide substantial funds for the newly independent country in its early years.

Asked by the Herald in May if it was still SNP policy to remove Trident within the first Holyrood term of an independent Scotland, Ms Sturgeon said: "That would be our expectation and hope. But when you're dealing with nuclear weapons the responsibility of acting in a way that is safe is of paramount importance."

Pressed at the time about the lack of a functioning alternative site for Trident in UK waters, she said: "I suspect these are questions you have to put to the UK Government. I have made clear we would act in a responsible way and that would apply to timescale."

Asked if she considered a single five-year term for ousting Trident to be "hasty", she said: "I would like to see nuclear weapons out of Scotland as quickly as possible.

"What 'as possible' means will have to take account of the detail of these discussions. But there is nothing changed in terms of the  strength of my feeling and strength of my opinion in terms of the nuclear questions."

Professor Chalmers will be among the leading contributors in the next instalment of our Scotland's Future programme which will run from tomorrow to Sunday.

The series began in February with an in depth investigation of the prospect of an independent Scotland becoming a member of the EU, including the route and timetable of gaining accession.

The latest chapter will turn to what type of policies the new state may pursue in the fields of international relations, defence and security.

The political parties opposed to independence will set out their stalls arguing why they see the country's interests as being best met by remaining in the United Kingdom.

in the aftermath of Russia's full-scale invasion of Ukraine in February this year, international relations, defence and security are likely to have a significantly more prominent role in Scotland's constitutional debate ahead of any new referendum than before the vote eight years ago.

Responding to Professor's Chalmers comments, Stewart McDonald, the SNP's defence spokesman, said most Nato members do not have nuclear weapons and the "safe and swift" removal of Trident would be negotiated between the Scottish and UK governments. 

“The vast majority of Nato members do not have nuclear weapons, and an independent Scotland would be in the same position as those non-nuclear member states. Independent countries have the right to seek Nato membership on their own terms, as is currently the case with Sweden, a non-nuclear weapon state," he said.

"Nato membership for an independent Scotland would maintain the alliance’s territorial integrity in a key strategic area – so the idea that Nato would choose to make itself smaller by excluding Scotland makes no sense from a strategic perspective."

He added: "The safe and swift removal of Trident from Scottish waters will be negotiated with the UK government after a Yes vote. No action would be taken which would jeopardise the security of the United Kingdom or any other Nato ally.

"The SNP has been clear that, as a party that wishes to see Scotland succeed as an independent member of the international community in Nato and the EU, we will be active participants in the ongoing debate about security and cooperation and play a meaningful role on the international stage."

Professor Juliet Kaarbo, co-director of the new think tank the Scottish Council on Global Relations, as well as the Chair of Foreign Policy at Edinburgh University, Professor William Walker, of the School of International Relations at St Andrews University, David Clark, former advisor to the late Foreign Secretary Robin Cook and Anthony Salamone of the Europa Institute will be among the scholars and analysts who will be contributing to the series over the coming days.

Subjects considered include can Scotland be a global leader, how many embassies would an independent Scotland have, what would the country's conventional military look like and when would they be deployed.