IN the last month or so, the polls started to become rather disappointing reading for the Yes side.

The last five polls all suggested Yes support was either static or had actually fallen back a little. With time beginning to run out, this was not a message the Yes side wanted to hear.

But today, the Yes side receive what looks like remarkably good news from a company, TNS BMRB, that has hitherto been relatively conservative in its estimate of the Yes vote.

Once the Don't Knows are left aside, TNS BMRB's latest poll puts Yes on 44 per cent, no less than three points up on the 41 per cent figure the company has recorded on six out of seven previous occasions this year, including in its last poll in the middle of June.

The Yes side have apparently made particular progress in securing the support of voters who voted Labour in 2011, up from an average of 21 per cent during the previous three months to 28 per cent now. Winning over such voters has long been a key objective of the Yes campaign - though also important is the fact that the proportion of 2011 SNP voters who are unwilling to back Yes has fallen back too.

But the Yes side continues to be dogged by the gender gap. Only 40 per cent of those women who are willing to say how they will vote state that they will vote Yes, compared with 47 per cent of men.

And the Yes side should remember that one poll does not make a summer. Occasionally the figures in an individual poll shift as a result of chance.

We will need other polls to confirm today's trend before we can safely conclude the race really has narrowed. But in the meantime Yes activists will have a bit more of a spring in their step.

l John Curtice is Professor of Politics at Strathclyde University