Scotland's government on Tuesday drew the battle lines for a historic tussle with London as it announced plans to hold a second independence referendum on October 19, 2023.
Addressing the Edinburgh parliament, First Minister Nicola Sturgeon conceded that her devolved administration may lack the power to call the vote without London's approval.
To ensure legal clarity, it will seek an opinion from the UK Supreme Court before it asks voters: "Should Scotland be an independent country?"
The phrasing of the question was the same as Scottish voters were asked in 2014, and Sturgeon said her government would press the case anew with "commitment, confidence and passion".
Eight years ago, Scotland voted to stay in the United Kingdom, and current polls suggest Scots remain evenly divided on the question of independence.
Prime Minister Boris Johnson's UK government says the 2014 plebiscite settled the matter for a generation.
Speaking en route from Germany to a NATO summit in Spain, Johnson vowed to study Sturgeon's plan and "respond properly".
But he stressed that "I certainly think that we'll be able to have a stronger economy, and a stronger country, together".
Sturgeon's Scottish National Party (SNP) says the UK's divorce from the European Union, following a 2016 referendum, has transformed the debate. Most Scottish voters were opposed to Brexit.
"What I am not willing to do, what I will never do, is allow Scottish democracy to be a prisoner of Boris Johnson or any prime minister," Sturgeon said.
The SNP wants to take an independent Scotland back into the EU but, mindful of Catalonia's abortive bid to break away from Spain, is aware that international backing hinges on the process remaining lawful.
Sturgeon stressed the "consultative referendum" would only proceed with the approval of the UK Supreme Court.
A vote in favour of independence would still need approval from both parliaments in Edinburgh and London before Scotland could formally break away.
If the UK Supreme Court rules that the Scottish government lacks the power to hold the vote without London's consent, "it will be the fault of Westminster legislation, not the court", she said.
In that scenario, the SNP would use the UK's next general election due by 2024 as a "de facto referendum" on independence, she added.
"Either way, the people of Scotland will have their say".
The SNP's opponents, including the Conservatives and Labour, say Sturgeon is fixated on holding a second referendum instead of on more pressing policy matters.
"We won't play Nicola Sturgeon's games, we won't take part in a pretend poll when there is real work to be done," Scottish Conservative leader Douglas Ross said in the Holyrood parliament.
Sturgeon's statement came as Queen Elizabeth II made an unexpected appearance at "Holyrood week", an annual series of ceremonial events in the Scottish capital.
The 96-year-old monarch has been in poor health, and surprised many by making the long trip north.
As head of state, the queen is politically neutral, but the Daily Telegraph said her visit to Edinburgh "packs an ever-so-polite political punch".
"Without speaking - and indeed almost without moving in public - she embarked on just the sort of show of soft diplomacy she has spent 70 years perfecting," the newspaper said.
In 2014, ahead of the previous independence referendum, Queen Elizabeth told well-wishers near her Balmoral estate in northeast Scotland: "I hope people think very carefully about the future".
Scotland voted by 55 to 45 percent to remain in the UK, after then British prime minister David Cameron agreed to make the result of the vote legally binding.
The Supreme Court confirmed it would consider the new legal bid, and would schedule a hearing "in due course".
Jonathan Sumption, a former Supreme Court justice, said that Sturgeon was charting "a very difficult course".
The UK's devolution settlement gives London a clear power of veto over any new vote, Lord Sumption told BBC radio.