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(This story, first published in May, has been updated toreflect recent events)
By Mike Peacock
LONDON, Sept 9 (Reuters) - An opinion poll showing Scottishindependence campaigners have a slim lead nine days before acrucial referendum has highlighted reasons for the wider worldand investors to pay heed to the Sept. 18 vote, which could seeBritain lose 5.3 million Scots.
Foreign governments and financial markets had long assumedScots would view independence from the United Kingdom as toorisky a leap but the sudden swing, confirmed by another surveyshowing the two camps neck-and-neck, has exploded suchcomplacency.
Losing Scotland would likely weaken Britain as a power, dentits self-confidence and make it more introverted, increasingdoubts about its future in Europe.
"BREXIT"
A lot of energy has been expended arguing whether anindependent Scotland could join the European Union. The EuropeanCommission said on Monday it stood by its position that Scotlandwould have to leave the EU and re-apply for membership.
Even more telling could be Scotland's absence from thedebate about whether the rest of the country should remain partof the bloc, on which Prime Minister David Cameron has promisedto give voters the final say if he is re-elected next year.
Overall, Scots are far more pro-EU than the English and ifthey secede in 2016 they would not get a say in the proposed2017 referendum on Britain's place in Europe.
Without Scotland, the chances of England, Wales and NorthernIreland voting to leave the EU are greater. Scots may onlyaccount for around 4 million of the UK's 45 million voters butwith opinion finely divided, that could tip the balance.
U.S. President Barack Obama said in June the UK would bestronger and more robust if it stuck together and Washington hasmade abundantly clear it wants Britain to stay in the EU.
Scottish nationalist (SNP) leader Alex Salmond says thebiggest threat to Scotland staying in the EU is Cameron's pledgeto hold an in-out EU referendum.
POLITICAL INSTABILITY
Scottish independence would also alter the calculus fornational politics in the rest of the country.
The opposition centre-left Labour party has 41 members ofthe Westminster parliament in Scottish seats while thecentre-right Conservatives have only one. Take those out of theequation and the path for Labour to win power looks daunting.
"In Britain, it will mean the end of any chance of Labourwinning power," former Labour Europe minister Denis Macshanewrote on The Globalist website this week.
Whichever way the Sept. 18 referendum goes, Scots will stillvote in a British general election next year, raising anotheruncertainty. If Labour won, its government might lose itsparliamentary majority and fall within a year once its Scottishlawmakers go.
That loops back to EU membership since the Conservatives arecommitted to holding a plebiscite while Labour is not.
The irony is that the Conservatives have traditionally beenthe strongest defenders of the union and many would be aghast atindependence even though it gave their party a permanentelectoral advantage in what is left of the United Kingdom.
CAMERON'S POSITION
Cameron would face pressure to quit if he lost Scotland. Thefull name of his party is the Conservative & Unionist Party.
Compounding his woes, a parliamentary by-election in Octobercould deliver the anti-EU UK Independence Party (UKIP) a firstWestminster seat after the Conservative incumbent defected.
If Cameron were to go - he says he would not resign - therewould be a clamour among the many eurosceptics in his party, andthose who fear UKIP will cost them their seats, for a moreclearly anti-EU leader to take his place.
That in turn could harden the chances of a British exit if anew Conservative leader would not campaign to stay in the bloc.
Salmond pressed for a third question on the ballot paper -for more devolved powers. Cameron's rejection of that now lookslike a miscalculation as the main parties scramble to promiseScots more autonomy if they vote "No".
CONSTITUTIONAL QUESTIONS
Even if Scots vote to remain part of the UK, theconstitutional genie is out of the bottle. Scotland is bound toget more autonomy if it stays.
Wales would almost inevitably demand more powers of its ownand the so-called "West Lothian question" - why should Scottishand Welsh parliamentarians be allowed to vote on laws that onlyaffect England when English lawmakers cannot do the reverse -would come to a head.
English nationalism, hitherto confined to the right-wingfringe, could take off, requiring a full-blown overhaul of theUK's constitutional settlement.
INVESTOR UNCERTAINTY
For investors, there are many unknowns to ponder.
What share of Britain's debt would Scotland take? Would itretain the pound? How much would Scotland get of oil revenuesfrom the North Sea, estimates of which vary wildly? Would itfollow a different fiscal policy? Can it join the EU?
The pound has dropped more than 3 percent against the dollarover the past week as the polls have narrowed dramatically.
The SNP wants to keep sterling but that is opposed by allthe main political parties in London, creating uncertainty whichcould persist for the 18 months pencilled in for negotiatingdetails of a divorce.
What is certain is that minus Scotland, Britain would slipdown the ranks from being the world's sixth largest economy.
There could even be longer-term questions about whether itshould keep a seat on the U.N. Security Council and stay in theGroup of Seven major economies at a time when power is shiftingto the world's big emerging economies.
The UK economy is Europe's biggest destination for foreigndirect investment. Without Scotland those flows would fall andthe rest of the UK's current account deficit could rise to alevel that discomfits investors.
The British Treasury has said it would honour all existinggovernment debt regardless of whether Scots vote forindependence, a move aimed at preventing bond market volatility.
But Salmond has said an independent Scotland could walk awayfrom its share of the UK's debt if it were not allowed to usethe pound. That could make Scotland a pariah on the bond market.
Ratings agency Moody's has said an independent Scotlandcould expect an investment-grade credit rating but face higherborrowing costs than the rest of Britain. If negotiations on howto separate proved acrimonious, its rating would be lower.
Rival agency Fitch said the UK would need longer to recoverits triple-A debt rating if Scotland split away.
MONETARY POLICY
The Bank of England has not been drawn beyond saying it hascontingency plans in place for a "Yes" vote.
But investors have begun pushing back expectations of whenit will begin to raise interest rates given the uncertainty thatcould follow next week's vote.
The sterling overnight interbank average shows the markethad pushed back its forecast of a UK rate hike to seven months'time, compared with its expectation of six months last week.
"The implications of increased economic uncertainty,financial volatility and fiscal risk post-separation would mostlikely result in delayed BoE rate hikes and tighter bankregulation to manage systemic risk in a fragmented union," saidLena Komileva at G+ Economics.
BUSINESS TO VOTE WITH ITS FEET?
Though reticent to go public, a number of majorScottish-based financial companies could head south if Scotlandgoes it alone.
Royal Bank of Scotland said in June it wasconsidering its options should Scotland vote for independence,adding that the vote had created a great deal of uncertainty.
Banking sources told Reuters that Lloyds Banking Group is considering having its registered office in Londonrather than Edinburgh if Scotland breaks away.
There could also be a more unruly rush for the exits. "Inthe event of a "Yes" vote there is a significant risk of bankdeposits shifting abruptly out of Scotland," UBS said in a note.
Pensions heavyweight Standard Life has warned itcould move partly out of Scotland and oil giants Royal DutchShell and BP have said they want Scotland toremain part of the UK.
DEFENCE
Britain has four submarines carrying Trident nuclearwarheads at the Faslane naval base in Scotland. The SNP wantsnuclear weapons removed from an independent Scotland at theearliest opportunity.
Former British defence chiefs warned against such a moveearlier this year, saying it would cost billions of pounds, cutthousands of jobs and create resentment internationally.
At a time of heightened tension with Russia, NATO allieswill be concerned, although it would likely take years to movethe naval base.
The future of the nuclear submarines are seen by some as oneof Scotland's main bargaining chips in getting what it wants inthe 18 months of negotiations that would follow a "Yes" vote towork out how it leaves the United Kingdom.
SECESSIONISTS IN SPAIN, BELGIUM
Europe is watching keenly, none more so than Spain.
The government in Madrid has refused to let Catalonia hold avote on independence in November but the region has vowed topress ahead with a non-binding referendum anyway.
If that is blocked, Catalan President Artur Mas said hewould call an election as a proxy vote on independence.
Scottish secession would embolden Catalans and some Basques,as well as potentially Flemish nationalists in Belgium. That maybe one reason why officials in Brussels have told the Scots thatit would be difficult for them to join the EU. Newcomers have tobe voted in unanimously by existing member states.
NORTHERN IRELAND
Scottish independence could also destabilise NorthernIreland.
Though a 1998 peace deal largely ended decades of sectarianviolence, Northern Ireland remains deeply split betweenProtestants who mainly want to remain part of Britain andCatholics tending to favour unification with Ireland.
The unionists have particularly close links with Scotlandwhile those who favour uniting with Ireland could seize on aScottish "Yes" vote to press their claims more forcefully. (Editing by Paul Taylor)
