Turnout at May's assembly elections was 44%, and at last year's general election it was 66% in Wales. 

Professor Roger Scully from the Wales Governance Centre at Cardiff University says trying to predict the turnout for this referendum is much harder than for previous UK and assembly elections.

In terms of turnout for the UK as a whole, he said: "We could be looking at anything from 55% to 70%.

"Looking at polling evidence and interest in the TV debates, I suspect it could be mid to low 60s."

Daran Hill, political commentator, said: "The campaign has, to pervert Hobbes, been nasty, brutish and long. 

"It has not always brought out the best of either side but I strongly believe that posing the question was the right thing to do, regardless of how that has unnerved much of the establishment. 

"The appeals which have been made from both sides have been as fear-inducing as each other. 

"The question definitely needed asking, but whether the campaigns needed to be so scaremongering, personalised and unpleasant are questions that may linger for as long as the actual result."

A word of caution on that YouGov prediction of a Remain win from our guest expert from the Wales Governance Centre.

Professor Richard Wyn Jones, who heads the Wales Governance Centre at Cardiff University,says that the EU referendum is an event of global significance - if the UK votes to leave there will be questions about the future of the EU itself.

There are also obligations for the party system, and it is possible whatever happens tonight that we will see fundamental changes in that.

BBC Welsh Affairs Editor Vaughan Roderick predicts there will be big differences in voting patterns across the UK, which will not follow traditional party lines.

He also said there were many anecdotal suggestions that turnout will be high - with predictions in Scotland it could be over 70%

The short answer is we don't know.

The longer one is that the Electoral Commission, external predict that the Welsh results, announced on a local authority rather than a constituency level, will emerge between 01:30 and 04:00 BST, external.

If they're right, the first results might come from Merthyr Tydfil, Denbighshire, Blaenau Gwent, Neath Port Talbot or Wrexham.

The last one would be Cardiff, Ceredigion, Pembrokeshire or the Vale of Glamorgan.

Prominent figures in the Welsh Leave and Remain camps have spoken about their sides' chances as polls closed in the UK EU referendum.

Lord Hain, manager of the Welsh Labour In campaign, said the Remain vote was stronger than he thought.

But UKIP Wales leader Nathan Gill predicted Wales will vote Leave. 

The overall figures for Wales are set to be announced in Flintshire at around 04:00 BST on Friday.

Welcome to BBC Wales' EU referendum results service. Stay with us throughout the night for news, views and expert analysis. 

We'll bring you the latest from our Welsh Affairs Editor Vaughan Roderick and the head of Cardiff University's Wales Governance Centre Professor Richard Wyn Jones, who are both contributing to BBC Wales's results programme which has just got underway on S4C. 

You can watch the programme on iPlayer, S4C's Clic, external or on our sister service BBC Cymru Fyw. Politics lecturer Ed Gareth Poole is also with us to interpret the figures as the night progresses.

Image source, Getty Images