'Unimaginable' - ballot-box effects of 'yes' vote hit home

Supporters exchange views with each other at the Grassmarket in Edinburgh. Photo / AP

Scotland’s decision could well be bad news for Conservatives and Labour.

In the two-year Scottish referendum campaign, Whitehall and Westminster have been in denial about the prospect of Scotland voting Yes to independence. Suddenly it is a very real prospect and the London political establishment is anxiously thinking about the implications.

"The consequences, not just for England, but Wales and Northern Ireland, are unimaginable," one senior Whitehall official said yesterday.

This is not an obscure debate about more devolution. Some MPs fear the peace process in Northern Ireland, or at least order on the streets, could be jeopardised and there could be new demands for a united Ireland. There would inevitably be calls for a stronger Welsh Assembly, more devolution to the English regions and even an English Parliament. If Scots vote to walk out of the marriage, there is no guarantee of an amicable "velvet divorce". An angry public mood in the rest of the United Kingdom, especially in England, could push the political parties into rejecting a friendly split.

Cabinet ministers already describe the SNP's timetable as "completely unrealistic", when complex issues such as the Trident nuclear weapons base need to be resolved.

But it is now dawning on MPs that a backlash from English voters against the Scots could force the Government to take a much harder line than ministers expect.

If the Scots reject enjoying the "best of both worlds" - more devolution and the security of the UK - then why should the remaining UK do them any favours in the divorce settlement? Such pressures could force the Conservatives to take a hard line on the negotiations in their manifesto for next May's general election.

A Scottish breakaway would provide yet more ammunition for the United Kingdom Independence Party. If its leader, Nigel Farage, demanded a tough line in the talks, the Tories might have to match it. In turn, that could put pressure on Labour to follow suit.

Who will be leading the Tories at the time? David Cameron has dismissed the idea that he would have to resign after presiding over the end of the 300-year Union.

But Cameron critics on the Tory backbenches have started to discuss amongst themselves whether a Yes vote next week could be the trigger for a coup against him as party leader. Opinions are divided over whether this would be the right moment to strike. Some Tories want to wait until after next May's general election.

Would Cameron fall on his sword after a Yes vote? "I think his instinct would be to carry on and steady the ship," said a long-standing friend. "But if things got really awful, and there was economic turmoil, it might be different."

There is already speculation in Tory circles over who might succeed Cameron. The rumour mill suggests Chancellor of the Exchequer George Osborne would be ruled out because his nuclear weapon in the referendum campaign - that Scotland could not keep the pound - backfired on the No camp. London Mayor Boris Johnson is unlikely to return to Parliament until next May, so Commons Leader William Hague is seen as the most likely caretaker.

A Yes vote could provoke calls for next May's general election to be delayed, as there would be little point in electing 59 Scottish MPs for 10 months until "independence day".

Some Labour figures believe they would struggle to win another Commons majority without their solid block of Scottish MPs - 41 at present.

The gossip among Blairite MPs is that their hero could still "win" England, but that a left-leaning leader could not. A Yes vote could be very bad news for Opposition leader Ed Miliband.