So as Chris has just mentioned, the UK is a very important trading partner to the EU. Similar in size to America in fact. But if we were to leave the EU would that be enough to stop us from being kept out in the cold when it comes to trade? 

This has been a key battleground thus far in the campaign, and over the next ten weeks it is like to get even more air time. 

The Leave campaign jumped on ONS, external statistics showing that sale of goods to the EU is falling and our experts from the Leave campaign have argued tonight that the EU market is less important now than ever. 

But Remain put forward figures from Frontier Economics for London First, external that show that trade could fall by between £67 billion and £92 billion a year if we left the single market and opted for a free trade deal. And anyway, we might not get a free trade deal for a very long time. 

The point, as Chris Cook is about to tell you, is that neither side really know what will happen to trade if we were to leave the EU. 

Our expert guest Juergen Maier from Siemens just said he thinks the period of uncertainty if the UK leaves the EU would last a while...

It's been claimed in the past it would result in 10 years of uncertainty.

Would it? A few answers here.

David Grossman
Newsnight political editor

"When you ASSUME you make an ASS out of U or ME."

So goes that dreadful piece of American management jargon. But economic forecasting is all about the assumptions. What do you assume will stay the same what do you assume will change. 

Image source, Getty Images

The political danger of today’s Treasury document, external is that the assumptions make an ass out of George Osborne. It assumes, for example, that there is not one benefit to be had from leaving the EU over remaining. Not one. (In that way it feels a bit like the assumptions made for that other Osborne pet project HS2, where the business case assumed that no-one did any productive work on trains so every minute of the journey was wasted time.)

From the perspective of the leave campaign this is a godsend. They are able to portray it as alarmist fantasy, where a more nuanced analysis would be far harder to counter. It’s also angered many conservative backbenchers who think the chancellor has turned the Treasury into a branch office of the Stronger In campaign. 

Incidentally Osborne is polling lower than Corbyn in a recent “who do you prefer as prime minister” question from YouGov, external.  Osborne’s case was also undermined by Jeremy Corbyn who declined to give his support to the Treasury’s analysis and actually argued its central tenet that more free trade is better for the UK economy.  

With Leave and Remain both using the statistics to prove their points, who can you trust? Newsnight, that's who! 

One good way of framing the economic argument is to think about what we stand to lose from leaving, mainly the trade deal we have with the EU. And what we stand to gain from leaving, in the trade deals we might be able to sign with the rest of the world. 

The Leave side argue we will lose very little if we leave, because we'll have a great trade deal with the EU. But is that true - Chris Cook has spent the day finding out, we'll be giving you the inside scoop here... 

So. So far we've looked at the trade deal with the EU but those who are campaigning to leave hope for better deals with the rest of the world meaning we'd need the EU much less than we do now.The question is whether the world will want to deal with us? 

Nicola Horlick became the youngest director of merchant bank SG Warburg aged just 28. Since then she has had a diverse career as a restaurateur, author, film producer and head of crowdfunding company Money&Co. Dubbed a ‘superwoman’ for juggling her career and bringing up 6 children. Expect Nicola to side firmly with Remainians, arguing that investment to the UK has already taken a hit because of the uncertainty.

Gerard Lyons is a respected British economist with an expertise in the world economy, global financial markets and on economic and regulatory policy. He currently serves as an economic advisor to Boris Johnson so it won’t be any surprise when he sides with the Brexiteers this evening. Expect him to echo is bosses views that financial services and the City would thrive in a post EU UK.

Farzana Baduel is the Founder and Managing Director of Curzon PR, a global strategic communications firm with offices in London, New York, Dubai and Delhi. Farzana comes to the debate with the perspective of someone who works across 3 continents. She's likely to argue that the UK can survive, and even thrive, without the EU because of the reputation we have in markets in Asia and North America. 

Juergen Maier was appointed Chief Executive of Siemens nearly 2 years ago and was appointed by Sir Vince Cable to be a Non-Executive Board member at the Department for Business, Innovation and Skills (BIS) shortly after. In the build up to the referendum he has been arguing strongly that close union with Europe lends us financial stability and economic opportunities and that stepping away from Europe is not in our national interest.

Dan Hannan is presumably referring here to the caginess of many Conservatives about their views on the EU referendum before the EU renegotiation. You can see what David Cameron achieved in his renegotiation (including the change on benefits) here

Evan just put a quote to Dan Hannan from one of his fellow Leave campaigners. Here it is, in full:

One of the main arguments that those that want to remain in the EU make is that it's easier for companies to do business if there's a single set of regulations across the whole of the continent. So if, for example, you are selling something in Spain, you know that you can also sell it in Britain without worrying about having to adapt your product to a whole different set of regulations.

Tweet us your thoughts and questions using #newsnight – we'll feature a selection here. Here's a couple of early ones...

Ian Katz
Newsnight Editor

It is hardly a secret that a battle over Europe is raging inside the Conservative Party but the government would rather it didn’t rage on your TV screens. For that reason No 10 has been operating a  “no blue on blue” rule when it comes to discussions like tonight’s Newsnight economy special. 

That means no ministers arguing against each other. Even tonight’s encounter between a minister and a prominent conservative Brexiteer is fairly unusual. It’s an understandable enough strategy: a victory for Remain that left the Tory party a war-ravaged ruin would be Pyrrhic indeed. But it does make casting debates like tonight’s a bit like a game of three dimensional chess. And it’s hard to see how the government will keep its ministers apart for another ten weeks.

First in Evan’s hot seat is Liz Truss, currently Secretary of State for the Environment, Farming and Rural Affairs. She is well and truly in the Remain camp tonight and is likely to argue that leaving Europe will lower UK wages, impact consumption of goods and leave people permanently poorer. She has previously said that voting Leave would be shooting ourselves in the foot.

Up against Ms Truss is Conservative MEP and notorious Europhobe Daniel Hannan. Hannan has been MEP for the South East of England since 1999, but cut his teeth as a speech writer for Michael Howard and William Hague. He is arguing this evening in favour of Britain leaving the EU.

The Remain side have kicked off their campaign by arguing the risks of leaving the EU. Dan Hannan, who will be arguing for Leave this evening, has written a piece, external on what he thinks are the risks of remaining in the EU. Amongst other things, he believes that by remaining in the EU, we risk paying for deeper European integration that the UK may not want in areas like welfare, and that we could be dragged into contributing towards bailouts for countries like Greece.

Hannan has been particularly vocal in his accusations that the PM and the remain campaign are ‘banging the table and angrily demanding the status quo.’ We can expect fighting talk from Dan Hannan tonight.

Evan just asked Liz Truss about how much we should mind about the Government forecast released today that says GDP would be 6% smaller in 2030 if we leave the EU than if we remain in it. He compared it to George Osborne's (or, to be precise the OBR's) forecasts since 2010. GDP turned out smaller than the Government expected too - funnily enough, by roughly the same amount.

There's a bigger point here which is about the volatility of forecasts. Look at how different the green line (forecast in March 2014) and the red line (forecast in July 2015). Only a year separates them, but they differ on the size of the economy by almost 2 percentage points.

During each of our EU Referendum specials we will be inviting two political heavyweights from each side of the argument to duke it out and win over our undecided voters. And of course all you undecided voters at home. 

This week Daniel Hannan MEP and Liz Truss MP enter the fray, going toe to toe with Evan on his specialist subject: The Economy. 

Image source, Newsnight

Ruth Lea articulates one of the economic arguments for Brexit - that we'd be more able to react to global events and change our regulations to suit the evolving economic environment if we don't have to negotiate everything with 27 other countries in the EU.