By Elisabeth O'Leary

EDINBURGH (Reuters) - The Friday morning after Britain voted to leave the European Union, leaders in London had little to say.

Prime Minister David Cameron resigned in a short statement. Boris Johnson, the face of the leave campaign, spoke for seven minutes. George Osborne, finance minister, was nowhere to be seen and would not appear in public for three days.

Four hundred miles away, Nicola Sturgeon, First Minister for the United Kingdom's northernmost nation of Scotland, appeared before the cameras, dressed in red.

Her message: Scots had voted decisively to stay in the EU. That may mean Scotland would split away from the rest of the country.

For the next 30 minutes, Sturgeon took questions from reporters in Edinburgh. The next day she held a crisis cabinet meeting and gave a statement. On Sunday she was on three television talk shows and three days later she traveled to Brussels to speak with EU politicians. On Twitter, she called Johnson the leader of "Project Farce" and criticized the uncertainty now faced by EU citizens living in Britain.

By addressing the acute political, economic and social crisis that has gripped the UK after the referendum, Sturgeon and her nationalist party have seized on a chance to revive their ambitions for Scottish independence. It was a project considered shelved nearly three years ago after Scotland voted to remain in the UK in its own plebiscite. Sturgeon has argued since then that many voted to stay in the UK because it guaranteed Scotland's EU membership. Now the Scottish parliament has given her a mandate to try to keep Scotland in the EU by whatever means possible.

"The UK that Scotland voted to remain within in 2014 doesn't exist anymore," she told BBC television. "There are going to be deeply damaging and painful consequences of the process of trying to extricate the UK from the EU. I want to try and protect Scotland from that."

It remains to be seen whether Scottish independence will happen. Splitting Scotland from the UK would end three centuries of shared history, upending another tight economic relationship shortly after a divorce between Britain and the EU. Scotland sells two thirds of its 76 billion pounds ($99 billion)of goods and services exports to the rest of the UK, excluding oil and gas.

But over the past two weeks, EU politicians have for the first time shown openness to Scotland's EU predicament. That could be a negotiating tactic for Brussels with London.

And the return of the Scottish cause shows how the EU referendum – originally pitched by Cameron as an opportunity to prove British unity with Europe while calming anti-EU lawmakers in his own party - is tearing at the social, economic and cultural cohesion within the four nations that make up the UK: England, Scotland, Northern Ireland and Wales.

An opinion poll published in Scotland's Sunday Post after the EU vote showed support for independence rising to 59 percent from the 45 percent who voted for it in 2014, a level roughly steady since then.

The referendum's aftermath has also created an opportunity for Sturgeon, a lawyer turned politician who two weeks ago was barely known outside Britain. She has put herself and her cause center-stage in Europe.

"She's a shining light, hardworking and with an integrity that the rest of the motley crew in British politics just doesn't have," said Ian Graham, a 48-year-old businessman from Kirkcaldy in Scotland. Graham said he didn't support independence last time, but may reconsider.

DOOR-TO-DOOR

Since her days as a teenager in Dr. Marten boots and listening to Duran Duran in Ayrshire, Western Scotland, Sturgeon has wanted Scottish independence. 

In 1987, at age 16, she knocked on the door of Kay Ullrich, a family neighbor in Dreghorn and an SNP candidate who would later become a lawmaker. It was a time when many local families had lost their jobs after factories closed. Sturgeon wanted to help campaign for the Scottish National Party (SNP), which argued that Scotland would be better off socially and economically if it unhitched from the rest of the UK.

At the time, SNP membership was around 2,000 nationally, said Ullrich, 73, who recalls Sturgeon as an ardent campaigner.

"We'd be in the pub already and her group would come in and say 'We'd have been here earlier but Nicola said 'let's do another street.'"

Sturgeon studied to be a lawyer and practiced until 1999, when she entered Scotland's devolved parliament. She had met then party leader Alex Salmond years before when he was a rising SNP star.

Salmond, considered smart but divisive by those close to him, asked Sturgeon to be his deputy when he ran, and won, the 2004 contest for party leadership. She stayed by his side until 2014 and the Scottish independence vote.

During the campaign, she debated the economic merits of leaving. Independence would mean Scotland had control of its own tax take and its own energy resources, most notably, North Sea oil, she argued.

Being around Salmond toughened her stance and rhetoric.

"When I was first in politics, women were very rare and the people around you tended to be middle-aged men and inevitably you do, subconsciously start to behave ... like a man," she told Reuters in an interview before the referendum. "It's only now that I'm older that I have had the confidence to be myself."

That confidence has earned respect from peers and constituents.

"There's no doubt that Nicola is focused. She can be ruthless and controlling (but) remains highly professional and enormously competent," said former Conservative Scottish lawmaker Mary Scanlon, a rival of Sturgeon's.

Constituents say Sturgeon is dedicated to political outreach, attending fundraisers with her husband Peter Murrell, who is the SNP's chief executive, and still finds time to call her mother every day.

Since she took over the party in 2014, SNP membership has risen fivefold. The party won 56 of the 59 Scottish seats in the national parliament in 2015.

The SNP's strong presence on the British political stage has helped to keep independence hopes alive at home, by giving a voice to Scottish issues. Scotland has about 9 percent of a total of 45 million UK voters and the devolved Scottish parliament decides health and education spending. From this year, it also has the power to set tax rates and bands after a deal to increase its clout offered just before the 2014 referendum.

 

TACTICS

In Brussels, Sturgeon has played a tactical game. The day before she went to the European capital on June 29, she won a rare mandate from a unified Scottish parliament to keep Scotland in the EU by whatever means possible.

In meetings with officials from across the political spectrum, including Martin Schulz, the German Social Democrat speaker of the European Parliament, she did not raise the issue of independence outright. Rather, she spoke about the disappointment of EU-loving Scots, according to several people who attended.

"She didn't use the referendum as an excuse to leave. She wasn't pushing independence at all," said an EU source who attended.

Not acknowledging the elephant in the room is a ploy for both sides, European officials say.

In the past, EU officials have been cold towards potential Scottish independence. That's because they feared igniting a nationalist fuse elsewhere in Europe, such as in Spain, where a drive for an independent Catalonia in 2014 brought hundreds of thousands of people onto the streets of Barcelona.

Now, however, Scottish independence is more appetizing in Brussels – if only as a negotiating tool to signal annoyance at London.

Sir David Edward, a Scot and a former judge of the European Court of Justice, said goodwill has been eroded by the years Britain has spent fighting for opt-outs of EU policy. European officials are "absolutely fed up to the back teeth" of the British, he told Reuters, explaining why many senior EU officials were more than happy to see Sturgeon.

What Scotland can do to retain EU membership remains legally unclear. But Edward says it is "almost all about political will." 

There are alternative relationships that could work for Scotland, short of full EU member status, including opt-outs or a trade agreement which would treat it as a separate entity.

Sturgeon's task at home is tough. She needs to balance keeping independence activists happy while trying not to scare off unionists, some of whom vote for her as the best defender of Scottish interests but oppose independence, according to party insiders.  

Willie Rennie, leader of Scotland's Liberal Democrats and a fierce opponent of secession, has agreed to support Sturgeon's campaign to curry favor in Brussels on condition that it is not a route to independence. 

"You don't get independence on the basis of a crisis. You don't wreak chaos upon chaos," he said.

(Additional reporting by Alastair Macdonald in Brussels; Editing by Guy Faulconbridge and Alessandra Galloni)