Italians are to vote on whether or not to make a series of major changes to their political system, in a referendum on Sunday that could trigger the resignation of centre-left Prime Minister Matteo Renzi, and potentially mark the beginning of the end for the eurozone.

What exactly are Italians voting on?

Reforms to about of third of the Italian constitution have already been approved by parliament, but a law originally designed to prevent a return to fascism requires changes that concentrate political power to be approved by the electorate too.

Italy referendum explained: What is it about and what would a No vote mean for the UK?

The exact nature of the proposed reforms is extremely complicated. So complicated, in fact, that a start-up has been offering pricey classes to Italians who want to properly understand the vote.

Essentially, Mr Renzi, who came to power two years ago, wants to streamline Italy’s political system so he can push through a major economic reform package. He wants to reduce the number of senators and limit the senate’s power relative to the lower house of parliament. He also wants to reduce the political power of Italy’s regions.

Few dispute that economic reforms are necessary: the Italian economy has essentially gone nowhere for 16 years and unemployment is high at 11.5 per cent. With the exception of Greece, Italy has had the worst performance of any eurozone country since the 2008 financial crisis.

But below the surface, a variety of political undercurrents are at play, with the vote becoming about more than the technical changes to the constitution.

Mr Renzi made the mistake of conflating his centrist leadership with a "Yes" vote, probably over-estimating his popularity in the process. Meanwhile right wing populists the Five Star Movement, led by comedian and Donald Trump admirer Beppe Grillo, have claimed the no position, portraying it as something of a protest vote against Mr Renzi's status quo.

What would a "No" vote mean?

Mr Renzi has said he will resign if the Italian public reject his reforms.

It is possible that the Italian president, Sergio Mattarella, could appoint another prime minister and a “technocratic” government could keep the show on the road for a while.

But if new elections are called for early 2017 it is conceivable that the Five Star movement could come to power.

The party currently has around 28 per cent support according to the polls, which is not far behind Mr Renzi’s Democratic party, which has 32 per cent.

An emphatic referendum victory might give Five Star Movement the momentum it needs to overtake.

Looking further ahead, some have said this could jeopardise the Euro. The Five Star Movement has said it would hold a referendum to decide whether Italy should leave the eurozone, and Italy is so large and economically important that many think the single currency itself would break up entirely if it did depart.

An exit from the eurozone would be a long, drawn-out process, but it is something which could run ahead of itself, leading to a sort of preemptive financial crisis.

And what would a "Yes" vote mean?

Success for Mr Renzi.

Despite being a vote in favour of change, a "Yes" vote is actually the closest option to a vote to maintain the status quo.

It would also be a vote of support for the Prime Minister, reconsolidating his mandate to lead, and a rejection of the right wing populism championed in Italy by the Five Star Movement and in other countries by the likes of Donald Trump and Nigel Farage.

So, which is it likely to be?

According to Italian law, polling had to stop on 18 November.

According to the final voter surveys, there was a projected 53.5 per cent to 46.5 per cent lead for the “No” camp.

But an enormous number, nearly a quarter, of Italians said they were still undecided, making it very hard to call. And a lot can change in two weeks.

This has been a of year of massive protest votes – in the form of Brexit and Donald Trump’s US Presidential victory. The Italian referendum result could be in keeping with this, but it could also work in Mr Renzi's favour.

According to some analysts, the Trump effect has frightened Italians, who are cautious about their country experiencing a violent shift to the right.

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Dr Paola Subacchi, the director of the International Economics Department at Chatham House, recently told The Independent: “People want to avoid the Trump effect in Italy. They are very concerned that the "No" voters include people like Five Stars Movement and the Northern league - lots of populists. They are both anti- Euro.

“They are both doing well at the moment, but there are people who were thinking of voting "No" at the referendum, who might change [their minds], because they do not like the groups and do not want to somehow legitimise these groups.”

She added: “People are not being asked whether to leave the EU or whether or not to leave the Euro or whether or not to have a far-right president with a lot of unpleasant features.