Scotland vote will be close Salmond will need to capture all the 'undecideds' | Toby Helm

A month ago, an opinion poll showing the no campaign six percentage points ahead would have been terrible news for Alistair Darling's Better Together team. Today, however, after an extraordinary week that began with a YouGov poll putting the yes campaign ahead for the first time, it will seem like manna from heaven.

Among those who are certain to vote and have made up their minds, the Opinium survey for the Observer puts no on 53% and yes on 47%. Among those certain to vote are a few 6% still to decide whether to plump for independence or the status quo.