What happens if Scotland votes Yes?

It's only one opinion poll - but the YouGov research giving the Yes camp its first ever lead has set minds racing about the consequences of Scottish independence.

Whatever the claimed benefits and drawbacks, there is no doubt that the challenges involved in separating the countries after more than 300 years are substantial.

And there are fears over whether Whitehall and senior politicians have done enough contingency planning - with some believing there has been complacency about a No victory.

The immediate aftermath of a vote for independence is likely to be characterised by confusion as the impending new reality is digested.

The companies affected by the Scottish referendum

Reassuring panicky financial markets and businesses, preventing a run on the Pound, and trying to ensure the economic recovery is not derailed will be priorities for the authorities.

Many MPs believe David Cameron would have to resign as Prime Minister immediately in recognition of his failure to secure the union.

Labour leader Ed Miliband would also come under intense pressure, as his party has spearheaded the No campaign in Scotland.

But there is a strong body of opinion that the main Westminster protagonists should remain in post to avoid adding to the turmoil - especially as there are no obvious replacements waiting in the wings.

By the time of the referendum the House of Commons will be in recess for the autumn conference season, lessening the potential for a vote of no confidence - although there could be demands for a recall.

The companies affected by the Scottish referendum

In many ways, a Yes verdict would merely mark a starting point, with 18 months of fraught negotiations to follow until Scotland's formal independence day of March 24 2016.

An early key decision for the Westminster politicians will be whether the general election scheduled for May next year can feasibly go ahead.

Currently Scotland returns 59 MPs to parliament: 40 Labour, 11 Liberal Democrats, six SNP, one Tory and an independent.

Polls are currently suggesting a tight race, meaning that any Labour government would almost certainly rely on Scots votes for a crucial eight months during negotiations over independence.

That would be regarded as completely unacceptable by many, with critics bound to suggest the Scottish were effectively negotiating terms with themselves.

The companies affected by the Scottish referendum

Even if there was a Conservative majority administration, they would still be obliged to take into account the views of an Opposition featuring an element that was soon to be 'foreign'.

Possible solutions to the quandary include holding the election without returning Scots MPs, or banning them from voting on key issues - both of which present major democratic and constitutional issues.

Another approach might be to postpone the general election until after independence day, potentially seeking the Queen's permission to form a government of national unity in the interim, in much the same way as happened during the Second World War. That too has its difficulties, and would require the repeal of the coalition's legislation fixing the parliamentary term at five years.

Pound plummets on independence fears

The negotiations themselves would be mindboggling in their breadth, requiring an organisational effort by the civil service not seen outside of wartime, as well as an army of external accountants and management consultants.

Among the more noisily heralded - although far from settled - rows would be Scotland's currency. The main Westminster parties have flatly dismissed the prospect of sharing the Pound, although Alex Salmond insists they will change their tune.

The new nation would be free to use the Pound without a currency union, but would have to give up control over interest rates and money supply, considered a serious drawback for a country with a large financial services sector.

Scotland could in any case be obliged to adopt the euro as part of terms for joining the European Union after independence. Senior European figures have suggested this could prove a difficult and protracted process, as members with secessionist movements such as Spain are nervous about setting a precedent.

Pound plummets on independence fears

The UK's assets and debts would also need to be divided, with Mr Salmond already having threatened that Scotland will not accept liabilities if negotiations do not go his way.

But the issues will range into every area of the existing UK's life, ranging from Trident nuclear weapons, military bases and policing of borders to migration, trade arrangements, reciprocal education and health provision, and state pension funding.

A whole new military force and diplomatic structure of embassies and ambassadors will have to be set up, and millions of new Scottish passports issued.

The new smaller UK would also potentially face questions about its continued status on the most exclusive international bodies - such as the UN security council.

Pound plummets on independence fears

Supporters of independence argue that all the upheaval is worth it to forge a Scottish state with a more representative democracy and complete control over its own affairs, including the ability to raise taxes, set welfare levels, and decide foreign policy.

Pro-unionists, however, insist they are ready to devolve many of those powers to Scotland within the UK framework - and argue that while both Scotland and the UK can succeed apart, they will fare better together.

With less than a fortnight until the referendum takes place, the arguments over the repercussions will only get fiercer.

Find out where sterling might move next

The companies affected by the Scottish referendum

Pound plummets on independence fears