What is holding Alex Salmond back? The central goal of the Scottish National Party since its formation in 1934 has been independence for Scotland by popular consent. This was out of reach until last week, because the SNP did not have the votes to get the necessary legislation through the Scottish Parliament, let alone through Parliament at Westminster. But after Thursday's result, the way is clear. The Scottish Parliament can pass a Referendum Act whenever Mr Salmond chooses. David Cameron and the Scottish Secretary, Michael Moore, have both, rightly, said that they will not stand in the way.
That is not to say that all possible complications are removed. There is the issue of the question on the ballot paper. The SNP is not seeking a blunt "yes" or "no" to independence, which would leave too many questions unanswered. The party would prefer to ask Scottish voters to give Alex Salmond and his team the authority to negotiate a route to independence – with the implication that Scotland would stay in the UK unless and until it reached a satisfactory settlement with Westminster.
Mr Salmond is also open to the possibility that there could be a second question on the ballot paper, giving the Scots the option of voting for greater devolved power for the Scottish Parliament as an alternative to independence. There is also an argument over when to hold a referendum. The SNP's opponents are now saying that if it must be done, it should be done immediately. Mr Salmond is thought to have calculated that he will have his best chance of success in 2014, when Scotland celebrates the 700th anniversary of the Battle of Bannockburn.
Another huge question, which would loom if Scotland were to vote "yes", would be what share of the Government's deficit should be borne by the Scots, given that much of it was run up rescuing those two Scottish banks, RBS and HBOS, from collapse, and that Scotland has for many years enjoyed a disproportionate share of public spending.
And, of course, the prospect of a Scottish referendum has political repercussions for the rest of the UK. There will be voters in the other component parts of the kingdom, including expatriate Scots, who will argue – not unreasonably – that breaking up the UK affects everyone, and therefore the referendum should be nationwide. Separation would no doubt give added strength to Plaid Cymru, but would be a serious blow to the Labour Party, which currently holds 41 of Scotland's 59 Westminster seats. The Conservatives , on the other hand, have only one – a circumstance which has not tempered the party's adamant opposition to a break-up of the UK.
Whatever the complications, this referendum will have to be held, and it will have to be before Scotland goes to the polls again in four years, as the SNP has promised. We know from the experience of the "Velvet Divorce" between the Czech Republic and Slovakia in 1993 that a state can divide itself in two without bloodshed or economic dislocation. If Czechs and Slovaks can separate amicably, so can the English and the Scots. After Thursday's SNP victory, there is no democratic case for denying Scotland the right to vote on separation.
What we do not know is how the Scots would vote. It is thought that a great many of those who backed the SNP last week did so because they wanted an administration that would stand up for Scotland's interests against the Government at Westminster. That is not the same as voting to break away. Alex Salmond and his party have earned the right to hold a referendum. Whether Scotland will want to follow them into the unknown is another matter entirely.