I think there will be a No vote on Thursday – possibly swung on the votes of people who say they are not Scots. If there is, the No campaign’s very late, panic-stricken promise of much greater devolution will have been pivotal. The main consequence of the devolution package, though – if enacted as promised – will be a constitutional crisis across the UK and quite likely the eventual independence of Scotland.

The Yes campaign has won over most Scots now, I think, and from a very low initial base. It’s been a remarkable effort. Meanwhile, the No campaign has been so weak that UK party leaders, aware that they cannot personally move votes in Scotland, have been forced to make promises they all know will lead to a constitutional cataclysm for the UK.

Even now, it’s clear the parties don’t agree on what should be in the ‘guaranteed’ devolution package. At the heart of this disagreement is the future of the Westminster voting rights of MPs with Scottish constituencies (let’s call them Scottish MPs for now). If Westminster, for example, loses all control over the NHS in Scotland – as the No campaign is promising – then the NHS in Scotland will become a different entity from the NHS elsewhere in the UK. It would then be intolerable to everyone for Scots to have any kind of say in how the NHS outside Scotland were run.

But if Scottish MPs lose all voting rights over health issues then a Labour prime minister who relies upon Scottish votes for his job (as the current bookies’  odds suggest for 2015) would not be able to legislate on health issues – that power would be available only to the ‘minority leader’. The UK has a parliamentary system of government, where the prime minister and government of the day are determined by who can carry a majority in the House of Commons. A presidential system, like the United States, can accommodate legislative haggling between the house ‘majority’ and ‘minority’ leaders, because the president is directly-elected as head of state. In the UK, the prime minister is defined by being the ‘majority leader’ – if you will – so a situation where the minority leader can legislate would in effect mean that the democratic leader of the country – the prime minister – would change according to subject.

‘No’ campaigners will say now that the UK constitution can accommodate such haggling – but they know this is simply a ridiculous notion. When a UK prime minister has a small majority, the opposition does everything it can to knock him or her out and create a new general election – that’s arguably the main job of the opposition. More significantly, though, there could be no true lines of democratic accountability – departments of state simply couldn’t operate if the prime minister of the day couldn’t carry legislation. There might be the theoretical option of a perpetual grand-coalition, but that would be closer to China’s political system than our own democratic one.

So, assuming a No vote, MPs will  – The No devolution offer goes – return to Westminster in October and almost immediately begin to legislate to remove the Scottish health system from Westminster’s purview. They (we!) will also legislate for the permanent (actually unconstitutional) guarantee of the ‘Barnet Formula’ uplift to the Scottish budget; we’ll devolve income tax raising powers and follow through on other radical promises. At present, the ‘West Lothian’ question is complicated by the fact that most bills passed through Westminster, even on devolved issues, impact upon Scotland in some way. In addition, many of the variables ‘devolved’ to Scotland are in truth controlled by London-based institutions (Royal Colleges, quangos, trades unions, etc) and of course the total Scottish budget allocation depends upon the (English) departmental spending decisions made by UK ministers in Whitehall. Sensible politicians (Lord Baker, Ken Clark most recently) have tried to propose practical mechanisms to take the West Lothian Question into account, but none of these could begin to survive the devolution package now being proposed by the No campaign.

For example, Baker and Clark have suggested that Scottish MPs could vote to introduce and finally pass legislation on ‘devolved’ issues, but would not vote on the changes made through the stages of legislation in between. This would make it clear who the prime minister of the day was but would also require him/her to negotiate with the ‘minority’ leader. However, the complete removal of the Scottish health system, along with a perpetual guarantee of much higher spending across the board in Scotland (regardless of need elsewhere in poorer parts of the UK) simply couldn’t accommodate any vote by Scots at all in devolved areas. And here’s an open-secret: UK General elections are not won through foreign, defence or international development policy – they’re decided upon by precisely the policy areas (Health, Education, Justice, Welfare, much taxation) the No campaign is proposing to hand over to Scotland lock, stock and barrel.

The devolution package presently proposed by the No campaign would in effect create an independent Scotland in all but name, but one which didn”t have to pay its share of national debt as required by full independence on Thursday’s Yes vote terms. Non-Scots would come to hate the Scots for their ‘deal’ and this would very quickly be reflected in the daily politics of Westminster. A terrible mutual antagonism between English (and Wales and Nothern Ireland) and Scots would push support for full independence well above the 50 % mark on both sides of the ‘border’, a new referendum would follow in a very few short years and Scotland would truly say goodbye this time.

Meanwhile, UK government – the No campaign has it – may be run by a prime minister elected following promises about policies  – health, education,  welfare – he or she couldn’t legislate over.

The No campaign has been driven to desperation because the Labour Party (Over 90% of Scottish Tories will vote No) has given too little priority to the politics of Scotland. While some SNP supporters will vote No, many more Labour supporters (up to a third) are saying they will vote Yes. The last-minute devolution package is therefore aimed at one group – Labour voters who intend to vote Yes. Jim Murphy, perhaps the most obvious person to lead the party Scotland, and his many talented colleagues presently based at Westminster might be able to save the union after a No vote if they move en masse, and immediately, to Holyrood. But reason tells me that the odds would still be very much against them If the No allies honour their devolution promise.

One option for the No campaign after a No vote is to renege on the devolution ‘promise’ – the first sign of this would be the idea of a delay until after the 2015 general election. The former would, of course, be morally unjust and would quite likely lead to civil unrest – the latter laudably absent from Scotland’s recent political history. And yet it seems clear that the devolution promise they’ve made is simply undeliverable. So, oddly, I find that I support the No campaign through instinct and emotion – while reason tells me that the cataclysm to come would be less, the process of change might be better managed, with a Yes vote now.