Scottish independence: What's going on in Scotland?

On 18 September, voters in Scotland will be asked in a referendum whether they want the nation to become independent from the rest of the United Kingdom.

Why is it happening?

The Wallace monument, built to honour Scottish freedom fighter William Wallace

The Scottish National Party, whose central aim is independence, won the 2011 Scottish Parliament election by a landslide, giving them a mandate to stage the vote.

On referendum day itself, voters across Scotland will head to polling booths to answer the Yes/No question: "Should Scotland be an independent country?"

The arguments for and against

The Scottish government, led by First Minister Alex Salmond, says the 300-year-old Union is no longer fit for purpose and that an independent Scotland, aided by its oil wealth, would be one of the world's richest countries.

He says it's time for Scotland to take charge of its own destiny, free from what he describes as the "shackles" of a London-based UK parliament.

On the opposite side of the debate, the UK government, led by Prime Minister David Cameron, says Britain is one of the world's most successful social and political unions.

The differing styles of Salmond and Cameron

What are the key issues?

Two major issues have emerged during the campaign - oil and currency.

Oil

North Sea oil and gas reserves (or more precisely the tax take from Scotland's share) are vital to the Scottish government's case for independence.

Mr Salmond says earmarking a tenth of revenues - about £1bn a year - could form an oil fund similar to the one operated in Norway, creating a £30bn sovereign wealth pot over a generation.

Mr Cameron says the North Sea has been a British success story - and now the oil and gas is getting harder to recover, it's more important than ever to back the industry with the "broad shoulders" of the UK.

The SNP's opponents also argue they're pinning future hopes on something that's eventually going to run out.

North Sea oil: Facts and figures

Currency

Currency has been the other big area of disagreement.

Under independence, the Scottish government wants to keep the pound as part of a formal currency union with the rest of the UK.

It argues this is in everyone's best interests, but the three main UK parties - the Conservatives, Labour and the Liberal Democrats - won't go for it, and say that whoever's in power after the next UK election will not agree to such a move.

This position came as the UK Treasury published analysis from its top civil servant, Sir Nicholas Macpherson who outlined several reasons why currency unions were "fraught with difficulty".

Currency debate explained

Do people want independence?

Hard to say with any great certainty at the moment, although recent polling has prompted both sides to say the result is now too close to call.

While polling trends generally indicate most people don't want independence, the "Yes" side says the momentum is now with them, after a a YouGov poll for the Sunday Times suggested that, of those who have made up their mind, 51% planned to back independence, while 49% intended to vote "No".

Polling expert John Curtice said that, for the past few months, it looked like the referendum race had stalled, with polling rarely departing very far from No 57%, Yes 43% (once the undecided were left aside).

But the professor of politics at Glasgow's Strathclyde University says the race may now have become a lot tighter.

You can keep up with the latest trends through the BBC's referendum poll tracker.

Who gets to vote

People aged 16 and over who live in Scotland get a direct say on the nation's future - as long as they're registered to vote.

There are some requirements, though. Eligible voters must be British, EU or Commonwealth citizens with permission to enter or stay in the UK.

That means the 800,000 Scots who live in other parts of the UK don't get a vote, while the 400,000 people from elsewhere in Britain who live in Scotland do.

Members of the armed services and their families serving overseas who are registered to vote in Scotland also get to vote.

What happens on 19 September?

On the day after the referendum, if there's a "Yes" vote, the Scottish government is likely to have a big party. After that, it will get down to the process of negotiating with the rest of the UK.

Mr Salmond wants to declare "Independence Day" in March 2016 with the first elections to an independent Scottish parliament in May. But, first, an agreement will have to be reached with what remains of the UK on issues like Scotland's share of the national debt.

However, if there's a "No" vote, the UK government is likely to have a big party, then turn its attention to the issue of giving more powers to the devolved Scottish Parliament.

The Liberal Democrats have been considering this issue the longest, and a commission led by former leader Sir Menzies Campbell, says there is now growing agreement among the pro-Union parties that the Edinburgh parliament should get significant new financial powers, like increased responsibility over tax-raising.

Let's end with a history lesson

Thanks to the 1995 Hollywood blockbuster Braveheart, many people are familiar with the Scottish wars of independence, fought between the late 13th and early 14th centuries.

A series of events saw England's King Edward overpower the Scottish kingdom in 1296, before Robert the Bruce inflicted some serious payback in the battle of Bannockburn in 1314 - an event which has just reached its 700th anniversary.

Other key moments through the ages included Bonnie Prince Charlie's ill-fated invasion of England in 1745, culminating in defeat at Culloden the following year.

Despite various challenges, Scotland is generally regarded to have asserted its independence from about 843, until the official unification with England took place in 1707.

At the time, the view was that Scotland was desperate for cash, but opponents of the move were outraged by claims that the Scots who put their names to the Act of Union were bribed.

The episode moved Scotland's Bard, Robert Burns, to write: "We are bought and sold for English gold. Such a parcel of rogues in a nation."

The Scottish government now hopes to write another chapter in Scotland's history.