ALEX Salmond was clear during First Minister's Questions this week: Scotland could negotiate independence from the UK well within the 17-month timetable proposed by his Government.

The average length of time to achieve full independence, after a decision was taken, was 15 months, he said. And he went further, telling MSPs: "It is difficult to understand why Scotland and the UK, as developed democracies, could not achieve a much quicker timetable."

The 15-month average cited repeatedly by the Government is based on a list of 30 countries which have become UN members in their own right since 1960.

It's worth noting at the outset that one of them, Vanuatu, has twice officially been named "Happiest Place on Earth" since gaining independence from joint British and French administration in 1980.

But it's also worth asking how relevant many of the countries are to Scotland's particular circumstances. Vanuatu may have been named the New Hebrides when it was "discovered" by Captain Cook but there the similarities seem to end.

The tropical paradise's 220,000 inhabitants gained independence not following a referendum overseen by the Electoral Commission, but amid an uprising known as the Coconut War. A political party based on an ancient cargo cult is still represented in parliament.

Vanuatu is not a special case. The Scottish Government's list also includes the Pacific island countries of Samoa, Kiribati and Tuvalu (population: 10,000). Most of the others are African nations emerging from colonial rule. Of the five European countries only two, Estonia and Slovenia, are members of the EU.

Of course it's easy to highlight the cultural differences between Scotland and Vanuatu, or East Timor, or Togo, or the Comoros, or Djibouti, or most of the other recently independent states.

But there is a serious point and it was well made by constitutional expert Alan Trench, of Edinburgh University. Most places on the list, he argued, had the machinery of a state in place before they achieved independence (albeit operating in the shadow of a governor's mansion).

They did not have to disentangle the shared functions of a much more developed state, so they provide no reliable evidence that Scotland and the UK could separate in less than a year and a half.

A three-year timeframe from referendum to independence day is Mr Trench's best guess, and he is working on the assumption that the UK, not just Scotland, would want to conclude negotiations as quickly as possible.

The Government's 16-page transition timetable took Holyrood by surprise when it appeared on Tuesday. It was seen as a hasty response to the Electoral Commission's recent call for greater clarity on the post-referendum process but, looking ahead, its real job was to persuade voters that independence and EU membership could be achieved smoothly, seamlessly and in time for the next Holyrood election in 2016 if Scots vote Yes next year.

On Monday the UK Government is almost certain to say exactly the opposite. Scottish Secretary Michael Moore is set to publish a paper on the constitutional legalities required for Scotland to separate from the UK and join the EU. It is unlikely to play down the difficulties.

There is growing speculation the document will argue that Scotland would not, as the SNP claims, be able to negotiate EU membership whilst it remained part of the UK.

If that's the case, it would complicate independence talks between Scotland and the UK because important EU-wide reciprocal arrangements – on access to health care, welfare and pensions, for example – would not apply and would have to be negotiated bilaterally.

The whole row over an independent Scotland's membership of the EU, which dominated the latter part of last year, looks set to erupt once more.