About 12,000 Protestant unionists, including contingents from Northern Ireland, marched through Edinburgh's Old Town today in an emotional show of support for keeping Scotland in the United Kingdom.

With pipe and drum bands, bowler hats and orange sashes, the marchers said the referendum on Scottish independence, which takes place this Thursday , threatened their culture and history.

Organized by the Orange Order of Scotland, the march demonstrated that the anti-independence campaign could count on a solid, substantial, bloc of votes in Glasgow, Scotland's largest city and the main battleground of the campaign.

But it also injected a sectarian element with a bitter and sometimes violent history into the campaign. The Order is linked to the Northern Ireland Protestant "loyalist" organizations and many lodges had crossed over the Irish Sea for the event.

Rivalry between Catholics and Protestants - famously manifested by supporters of Glasgow's Celtic and Rangers soccer clubs - has often been a blight on Scottish society.

The decision to march has been controversial. The official pro-union Better Together campaign had said the parade had nothing to do with them. However, spectators displayed signs, badges and stickers bearing the campaign's slogan - "No Thanks".

Some marchers chanted "No Surrender" - a slogan from the conflict in Northern Ireland.

A Scottish vote for independence could force England and Northern Ireland to reassess their own constitutional relationship, an issue which haunts the delicate peace between Catholics and Protestants in the British-controlled province.

But the atmosphere today was generally festive as marchers filed through Edinburgh's Old Town which dates back to the Middle Ages. Many people on the march or those lined up along the streets carried Union Jacks as well the Scottish saltire flag.

"Proud to be British, Proud to be Scottish," banners read.

Independence supporters say it is time for Scotland to rule itself, free of politicians in London. "No" campaigners say that Scotland is more secure and prosperous as part of the United Kingdom, and the end of the union would destroy three centuries on bonds and shared history, as well as be an economic disaster.

Independence supporters kept a low profile during the march, although it passed some establishments with "Yes" banners hanging from the windows.

The Orange Order takes it name from Dutch-born William of Orange, who defeated Catholic forces of King James II at the Battle of the Boyne in 1690. Some banners depicted William on his horse.

Dedicated to defending the union and Protestant interests, it holds huge annual marches in Northern Ireland and Scotland that in the past have erupted in violence.

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