Scots will on Monday be given 100 weeks to make the "most important political decision in 300 years" of Scottish history when David Cameron and Alex Salmond sign a deal to stage a legally watertight referendum on independence. 
 
 In a move that could herald the biggest shakeup in the UK since Irish independence in the 1920s, the prime minister will fly to Edinburgh to settle the terms of a one-question referendum to decide Scotland's future in 2014. 
 
 The announcement, dubbed the Edinburgh agreement by Salmond's officials, was hailed by the Scotland secretary, Michael Moore, as the biggest political decision in 300 years – a reference to the two Acts of Union that bound the kingdoms of England and Scotland in 1707. 
 
 Westminster and Holyrood, described by the prime minister as "Scotland's two governments", have both given ground to allow for a 35-clause deal that will give the Scottish parliament the power to hold the referendum, probably in the autumn of 2014. 
 
 Salmond, the Scottish first minister and leader of the Scottish National Party (SNP), has abandoned his unofficial campaign to add a second "devo max" question – a form of enhanced devolution that stops short of independence – after failing to win support for it in Scotland. The UK government has given ground by allowing the referendum to be held in 2014 – London had originally favoured next year – and not blocking Salmond from allowing 16- and 17-year-olds to vote. 
 
 Salmond, whose emphatic victory in the 2011 Scottish parliament elections paved the way for a referendum, said the agreement would allow the vote to be "made in Scotland". The first minister said: "The agreement I expect to reach with the prime minister is one which ensures that not only is the referendum made in Scotland, but that the fundamental right of the people of Scotland to choose their own future is respected by all. 
 
 "The agreement will see Scotland take an important step toward independence, and the means to create a fairer and more prosperous Scotland. I look forward to working positively for a yes vote in 2014." 
 
 Cameron, who is expected to emphasise Scotland and England's shared military history during his brief visit to Edinburgh on Monday, highlighted the UK government's continued say in Scottish affairs by saying Scotland's "two governments" had reached this historic deal. Cameron then mimicked Salmond's rhetoric by claiming the deal had delivered "the people's referendum". 
 
 "Scotland's two governments have come together to deliver a referendum which will be legal, fair and decisive. This marks the beginning of an important chapter in Scotland's story and allows the real debate to begin. It paves the way so that the biggest question of all can be settled: a separate Scotland or a United Kingdom? I will be making a very positive argument for our United Kingdom." 
 
 The leaders of "Scotland's two governments" will take part in an orchestrated event at St Andrew's House, the headquarters of the Scottish government in Edinburgh. They will sign the agreement with Moore and Nicola Sturgeon, the deputy first minister, who have negotiated the deal. 
 
 But Cameron will not hold a joint press conference with Salmond amid fears in London that the first minister will try to use his moment in the limelight to embarrass Cameron. "The first minister wants to attract as much attention as possible," one UK government source said. "We just want to bomb him with reasonableness." 
 
 Under the deal, MPs at Westminster will temporarily give the Scottish parliament the legal authority to hold the referendum, overseen by the UK Electoral Commission, but with a sunset clause which removes that power at the end of 2014. UK government sources said they were not prepared to allow Salmond to postpone the referendum if opinion polls suggested he would lose. 
 
 Under UK referendum legislation which is policed by the commission, Holyrood will be allowed to extend the vote to 16 and 17 year olds for the first time in a major vote in the UK. The Scottish parliament has already allowed them to vote in health board and crofting elections. 
 
 There are growing signs that Salmond's government will clash with the commission over campaign spending limits. A deal allowing Holyrood to set those limits was one of the final issues to be settled last week, but Salmond and the commission are at odds on how much can be spent. 
 
 His ministers fear the commission's proposal to allow all registered parties to spend up to £1.5m in total during the last 16 weeks of the campaign, in addition to separate spending by each official referendum campaign based on their vote at the last Scottish elections, will give the three pro-UK parties of Labour, the Tories and Lib Dems a significant advantage. 
 
 Despite being given £2m in donations towards independence, Salmond wants to limit spending by each of the parties to £250,000 in the final four months of the campaign, with the official yes and no campaigns limited to £750,000 each. 
 
 Both sides claim they have achieved their main goals in the talks, but the honours are divided. 
 
 Salmond has been forced to accept only a single – yes or no – question on Scottish independence and to agree to appoint the Electoral Commission to judge the fairness of the question, and to police spending and voting rules – a measure he heavily resisted last year. 
 
 Attempts by the first minister behind the scenes to build a powerful coalition between business leaders and civic organisations to add an electorally popular second option to the referendum, for much greater powers for the Scottish parliament within the UK, failed because it lacked support. Salmond wanted the "devolution plus" option added to the referendum in case he lost on the independence vote. 
 
 The latest opinion polls suggest support for independence is sliding: a TNS BMRB poll last week said there is now a 25-point gap between support for remaining in and leaving the UK. Senior SNP sources admit their private polling too shows that staying in the UK is currently more popular. 
 
 Along with giving way on votes for 16- and 17-year-olds, Cameron has conceded that the poll will be held at a time of Salmond's choosing: autumn 2014 rather than next year, his original preference. 
 
 Alastair Darling, the former Labour chancellor, who now leads the pro-UK Better Together campaign, said he would have preferred the vote to be in autumn 2013, and objected to extending the franchise to 16- and 17-year-olds as a one-off, rather than as a permanent measure. Salmond wants the vote in 2014 largely because Scotland is hosting several high-profile cultural and sporting events that year. 
 
 Salmond also believes the UK government's spending cuts will be so unpopular by then, and the Tory-Lib Dem coalition so divided, it will strengthen Scottish support for independence. 
 
 Salmond will host a second "year of homecoming" and a clan gathering for expatriate Scots as the country marks the 700th anniversary of the famous Scottish victory over the English as the Battle of Bannockburn. In the summer of 2014, Scotland will host the Commonwealth games and the Ryder Cup golf competition between Europe and the US. ||||| EMAIL 
 
 Zarah, Aberlour 
 
 emails: Voting will be easy when we get some facts on the table. Alex Salmon needs to open up about his plans and allow the people of Scotland to make an informed choice. We need to be clear about Europe the Monarchy and Sterling. I so want to be able to say yes like most but we need clear answers.
– The countdown to Scotland's referendum on independence from the UK officially began today, as British Prime Minister David Cameron arrived in Edinburgh and signed an agreement with Scottish leader Alex Salmond, the BBC reports. The deal settles the terms of the 2014 referendum on whether to end the 305-year-old union, according to the Guardian. Cameron has accepted Salmond's timing of the vote—the 700th anniversary of the Battle of Bannockburn—and his demand to allow 16- and 17-year-olds to vote, while Salmond has agreed to drop his demand for a question on limited devolution, leaving Scots with a straight yes or no vote. "The agreement will see Scotland take an important step toward independence, and the means to create a fairer and more prosperous Scotland," Salmond said ahead of the meeting. "I look forward to working positively for a yes vote in 2014." But polls show that no more than 40% of Scots currently favor independence, and the British government argues that an independent Scotland would struggle without funding from London, Reuters reports.