Analysis: Poll shows real momentum for Leave, but undecided still the key unknown

If the 20 percent which this poll says remain undecided – and that number actually increased slightly from the previous month’s poll – were to be split evenly and between both camps, that would equate to a final split of 60-40 in favour of Remain in Northern Ireland.

Such a narrow result in a part of the UK where support for the EU was believed to have been strong would have been predicted by few people at the start of the campaign.

But rather than split evenly, in the final days of a referendum campaign more of the undecided are likely to plump for the status quo – in this case, Remain – rather than take what is generally perceived to be a riskier option.

That was what happened in the Scottish referendum and could mean that the 20 per cent undecided actually split something like 15-5 in favour of Remain.

Nevertheless, there is some evidence in this campaign that – in line with an unpredictable global political climate which has seen the shock emergence of Syriza, Jeremy Corbyn and Donald Trump – the old rules are not necessarily applying.

In fact, over the last week it has been the Leave camp which has been gathering real momentum.

Turnout will be crucial, with the belief that Leave supporters are more motivated and therefore benefit from a low turnout.

With many voters still open to backing either side, there could yet be a pronounced swing back towards Remain in the final days. But it’s getting very late.