Pollsters relieved - but who said it was 'too close to call'?

The relief of the pollsters will be as heartfelt as that of Unionist politicians at the decisive result of the Scottish referendum. All seven major polling companies whose surveys I have been following these past few weeks can say they picked the winner.

But although they foresaw a No win, they underestimated the ten-point margin of victory - 55 per cent No to 45 per cent Yes after all the votes were counted this morning. Their constant urging that it was "too close to call" appears, in hindsight, to be a misjudgement.

The final eve-of referendum polls by Ipsos-MORI and Survation had suggested a No victory of 53 to 47. A final polling-day survey by YouGov yesterday, when they recontacted those they had questioned earlier in the week and asked how they actually voted on the day, predicted a No victory of 54 to 46 – not bad, but still short of reality.

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• The Mole: Salmond and Miliband are the big losers

The greater-than-predicted winning margin suggests that those of us who suspected a "shy No" phenomenon were right to so. This the group I identified on Monday – Scots who concealed their intentions, possibly from family and friends as well as pollsters, because they felt awkward about seeming negative amid the excitement – some would say intimidation – promoted by the Yes campaign.

But, of course, another explanation could be that the pollsters simply under-estimated the No vote all along and/or miscalculated their "weighting" methods.

It was the release of YouGov's election day prediction that saw the pound climb sharply on currency markets last night. Yet the pound only fell in the first place because of YouGov's famous "shock poll" in the Sunday Times of 7 September which showed the Yes campaign suddenly going into the lead by two points.

That poll didn't just hit the pound – it had a profound effect on the campaign, galvanising the Better Together team, getting Gordon Brown back on the road and – most controversially – bringing a promise from the three party leaders in London of further devolution of tax and spending powers to Edinburgh in the event of a No victory.

In the pollsters' defence, it can be argued that whatever their individual methodology, they tended to come out with similar results, suggesting they were picking up the same shifting opinions.

But the debate about that 7 September poll will continue: did it point up a genuine Yes lead or, as Andrew Neil put it on BBC TV early this morning, did "one rogue poll" cause David Cameron, Nick Clegg and Ed Miliband to make promises they are going to find hard to keep?