David Cameron enters probably the most critical fortnight of his premiership with his aides juggling two alternative frenetic schedules.
The simple one takes him next week to New York for vital meetings at the UN on combatting Islamic State (Isis) and climate change; the other keeps him cloistered in London dealing with the economic and political fallout from a stunning vote should the Scots go for independence.
Both diaries contain unprecedented perils, and Cameron will not know which schedule to activate until early on Friday morning, when the final result of the Scottish referendum can be absorbed.
If it is a yes vote, Cameron has two choices: either to convene parliament immediately at the weekend, or instead to wait until Monday, by which time the markets will have reopened after what will have already been one hectic day of currency trading on Friday.
Both options have their merits, but a delay until Monday has the advantage of giving Cameron time to talk to Alex Salmond, his key advisers and the opposition on how to prevent the wreck of the ship of state.
A Monday recall of the Commons would also require Labour either to delay or shrink the first full day of its annual conference in Manchester. Labour will not discuss any contingency plans it has, just as Downing Street keeps up the pretence that it has none in the event of a yes vote. However, senior Labour figures recognise that a yes vote would blow its conference sideways, and would require a totally different speech by Miliband on Tuesday next week. Labour has been planning to make domestic issues such as the NHS the centrepiece of its conference, but the momentous political and economic consequences of a yes vote would dwarf all else.
Miliband would also have to gauge the extent to which he would seek to pin the blame for the breakup of the UK on Cameron's misjudgments and the inadequacies of the Better Together campaign. Inter-party recriminations may not meet the scale of the existential crisis, and it would not be difficult for Tory MPs to counter that Labour should shoulder the blame for losing touch with its Scottish working-class base.
Labour is likely to wait to observe the mood on the Tory benches before tabling a vote of no confidence in the prime minister, a vote that might prompt a change of PM or even a general election. Cameron would be politically weak, and possibly fatally wounded, but traditionally a vote of no confidence tabled by the opposition has the effect of suddenly reuniting the governing party. It will be left for more junior Labour figures to highlight the errors Cameron made in paving the way for the referendum.
Instead Miliband is likely to respond to a yes vote by embracing a form of English nationalism, including a need to rebalance power between Whitehall and the English cities, and regions.
With the blessing of the shadow chancellor, Ed Balls, Miliband is also likely to adopt a strong negotiating position against the Scottish government on the terms of separation.
If there is a bidding war after a yes vote, it would be between Labour and the Conservatives on which party is toughest with the Scottish government. Parties will set out their red lines on currency union, border security, Trident, pensions, banking and financial regulations, and the national debt. There will be few English or Welsh votes in 2015 in adopting a reasonable tone with Salmond.
In the event of a narrow no vote, Cameron will take a second to breathe a sigh of relief, before triggering a different but equally frenetic timetable. His immediate goal in Scotland would be reconciliation between yes and no, and to trigger the hasty timetable for extra devolution in Scotland set out by Gordon Brown at the height of the establishment panic that the nation was heading towards the UK exit. At the same time he will have to acknowledge the seething mood of English nationalism expressed in the calls for an English Parliament being led by John Redwood.
But Cameron will also bring the fight against Isis to the fore. On Tuesday, the day of Miliband's setpiece party conference speech, he will fly to New York to the UN secretary general's special summit on climate change, a meeting designed to set the agenda for the global climate change deal due to be negotiated in France in 2015.
The day after, Barack Obama will chair a meeting of the UN security council. It is not expected that any resolution endorsing military action against Isis in Syria will be tabled, an issue that would trigger divisions with Russia and Iran. The focus will be as much on co-operation to stop the flow of foreign fighters into Syria and Iraq, an issue that requires greater co-operation from Turkey.
Cameron is under pressure from some backbenchers to detail what more the UK will do militarily to help the coalition against Isis in Iraq.Britain is already sending arms to the Kurds and flying Trident reconnaissance operations over Iraq with planes flying out of Iraq.
But the prime minister has been cautious for three reasons: the Scottish referendum; the need for the US secretary of state, John Kerry, to solidify an anti-Isis coalition both among Gulf states and within Iraq; and finally an inchoate fear that he will again get himself ahead of the mood among his MPs, as he did last year on Syria.
So No 10 has guided strongly against an imminent shock-and-awe campaign of air strikes against Isis, even though this will frustrate parts of British domestic opinion infuriated by the threats facing the British hostage Alan Henning. The foreign secretary Philip Hammond said openly yesterday the UK does not know his Henning's location, but vowed Britain will play a leading role in the coalition against IS in Syria, a clear hint that the UK will step up its military support.
Cameron knows support for UK involvement in air strikes against Isis in Syria without an invitation from the Syrian government is more problematic, militarily and legally.The prime minister has two legal defences ready. First he has said Isis represents a direct threat to the security of the UK, and second the Syrian government is illegitimate, precluding the need for an invitation to strike by air from President Assad.
But the doubts on Tory benches are practical as much as legal. Cameron has yet to convince his party that a campaign to crush Isis inside Syria is practical, does not lead to civilian casualties and will strengthen the moderate Syrian opposition, rather than Assad. He is also wary that Labour at the last minute might set conditions that would make their support impractical. But all that at least represents the luxury of a problem some weeks away, and for Cameron right now that is a lifetime away.
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