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As the Scottish National Party opens what could be its last conference before the dream of an independent Scotland is finally realised, its leader Alex Salmond will demand one final big push to orchestrate the historic division of the United Kingdom.

But the SNP's battle cry to rally the 'Yes' vote in the referendum conceals a profound split in Scottish society itself: the toxic divide between Protestants and Roman Catholics.

Indeed, the outspoken MP George Galloway has issued a bleak warning to those Catholics in Scotland who might be toying with the idea of divorcing from the "Auld Enemy" - England - on 18 September: Be careful what you wish for.

So anxious is Galloway about the future for Catholics in an independent Scotland that instead of forming an unholy alliance with the Better Together camp he is imploring Scots to Just Say Naw and stick with the 1707 Union.

Galloway, now Respect's MP for Bradford West, grew up in the Irish Catholic community in Dundee and believes Catholics will get a raw deal in the event the Scots vote to break up the United Kingdom.

"My own experience of growing up as a Roman Catholic in Scotland has led me to fear independence in Scotland," said Galloway.

"Of course, most Scottish people are not swivel-eyed, loyalist sectarians but there are a large number of them. A large six-figure number, and if I were living in Scotland as a Roman Catholic I would be worried about that."

Galloway has even hinted at pogroms and Yugoslavia-style ethnic cleansing in the event of a "Yes" vote – claims which have been energetically dismissed by a spokesman for the Yes camp.

"These claims are mere scaremongering and have little validity in a present-day Scotland," he said.

"The Yes campaign has support from across the spectrum – political beliefs and none, religious beliefs and none, and also include a wide range of national origins."

Even those in the 'No' camp have attacked Galloway for his blood-curdling vision.

Many Scots are outraged that Galloway seems to be stoking up the fears of Scotland's large Catholic minority, known as "Left Footers" by some Protestants due to the myth they used their left foot to dig potatoes in Ireland, from where many migrated in the 19th and 20th centuries. Yet it does seem Catholics still provoke hatred among "swivel-eyed, loyalist sectarians".

The late Catholic lawyer Paul McBride QC, who received death threats from rabid Scottish nationalists during his lifetime, once described sectarianism as the"most serious social issue in the country today".

A Modern, Forward-Looking Country?

Galloway recently published a book (Open Season) in which he contextualises the hate campaign directed at Celtic manager Neil Lennon, which included bullets and parcel bombs sent through the post and his family being given 24-hour protection. He was attacked on the pitch and had a furious row with Rangers manager Ally McCoist on live television; first minister Alex Salmond had to convene an emergency conference to discuss "Scotland's Shame".

However as the referendum nears, the SNP seems keen to draw a line under the tribal politics of the past.

An SNP spokesperson said: "[We] are committed to stamping out the scourge of sectarianism in Scotland, and the Scottish government has committed £9m per year on projects to tackle the problem, while establishing the Advisory Group on Tackling Sectarianism in Scotland to advise on the issue.

"An independent Scotland will be a modern, forward-looking country with a 21st-century written constitution based on the principle of equality. Among other things, it will get rid of the disgraceful anti-Catholic discrimination of the 18th century Act of Settlement, which is at the heart of the UK's constitutional arrangements."

Which all sounds very forward-looking, yet in many areas, particularly in the west of Scotland, people from the Scottish/Protestant and Irish/Catholic community barely interact. They live in different neighbourhoods, support different football clubs and drink in different pubs. If Scotland does go its own way on 18 September, will the two communities put aside their differences, or become more deeply entrenched within their own, without even a mutual loathing of the "Auld Enemy" to provide them common ground?

When last November a police helicopter crashed into the packed 'Catholic' Clutha pub on the banks of the Clyde, killing all three aboard and seven in the pub, the accident seemed to reveal Scotland – and Glasgow in particular – in a positive light, with locals coming together to rescue those trapped inside.

Yet within a few days, a darker aspect to Scottish society was exposed: vile messages about the accident led to several people being charged. One of these, Liz Bingham, daughter of murdered Northern Ireland Ulster Volunteer Force (UVF) leader John Bingham, asked if there were any "Taigs" – Catholics – inside the pub.

90 Minute Bigots

The historic links with Ireland go some way towards explaining what seems like Scotland's peculiar obsession with religious sectarianism, where three-hundred-year-old battles are celebrated in song at the football.

The charity "Nil by Mouth" was set up in 1999 in response to the unprovoked murder of 16-year-old Celtic fan Mark Scott in Glasgow by Jason Campbell, the 'Gers-following son of a member of the UVF.

Nil by Mouth's Director, Dave Scott, originally comes from Antrim in Northern Ireland and though he agrees Scotland doesn't have quite the same intensity of hatred as his homeland (Irish comedian Dara O'Briain calls Glasgow "Belfast-Lite") he does believe education important whichever way the electorate decide on 18 September.

"Sectarianism isn't the biggest issue facing Scotland, but it shouldn't be swept under the carpet. Sectarianism will continue to be an issue whichever way people vote. Since sectarianism became a hate crime in 2003 there have been 7,000 arrests for sectarian hate-crimes."

When most people think of the sectarian issue, they tend to think of football, and in particular the history-drenched "Old Firm" games between Rangers – the "Huns" - and Celtic – the "Tims". With Rangers traditionally being seen as "Protestant" and Celtic "Catholic" the rivalry has been one of the most vicious in world football – witness the reaction when Paul Gascoigne jokingly played the pipes in front of incensed Celtic fans when he played for Rangers in 1998. Yet many dismiss those who scream abuse at matches as mere "90 minute bigots"– a suggestion that cuts no ice for Scott:

"You wouldn't shout 'nigger' and be dismissed as a '90 minute racist'."

In 2011 the SNP used their majority to pass the Offensive Behaviour at Football and Threatening Communications Bill in an attempt to clamp down on sectarian chanting at matches, but not everyone believes this is the best way to bring together the two communities, and some go even further, accusing Salmond of hypocrisy for banning football fans from singing about the Boyne and the GPO when he glorifies the Battle of Bannockburn.

As 18 September nears, old allegiances are being cast aside and surprising ones formed; many in the Catholic community seem worried about their future as a minority, albeit a large one, in an SNP-led, mostly Protestant nation; and some from the Rangers, Protestant community seem equally keen to say goodbye to the union – thought there are exceptions to the rule.

The Grass is Always Greener...

Dr John Kelly, lecturer in sociology of sport at the University of Edinburgh, believes the SNP, which used to be dominated by controversial figures like the party's former President and leader Billy Wolfe, who condemned the Pope's visit to Scotland in 1982, is now far more accepting of Catholics.

"It is true that the SNP have always had an uncomfortable relationship with 'sectarianism'," says Kelly in an email. "They rely on the votes from an electorate that is 17% (750,000) Roman Catholic and overwhelmingly Protestant (officially and those who would casually classify themselves as Protestant in a cultural sense). Indeed, this is probably why the SNP promise to retain the Queen - they fear losing some of the Protestant separatists/independence voters and believe that the Queen (with the Protestant symbolism she signifies in Scotland) will seduce sections of the Protestant voters."

Despite a great deal of hard work being done on the ground by community organisations there seems little doubt that in some areas the two communities are divided by religion, football and even colours. In Protestant Larkhall, green traffic lights are regularly attacked, the local Subway had to paint its usual green signage black and there are claims local youths attempted to set fire to the grass.

Whatever happens on 18 September, it will probably be a long time before green and blue unite to form the vibrant banner of a brave new Scotland.