The many thousands who were enchanted on Saturday night by Joseph Calleja’s rendering of Neapolitan classics at the Granaries in Floriana may well have enjoyed the evening and the spectacle without realising that staring us in the face (well, almost), there was something of crucial and actual importance.

The most popular songs in the Neapolitan repertoire date from very different days – the days when Naples was affluent, rich… and a capital city. We are talking here about Bourbon Naples, before Italian unification took place, as we are commemorating these days, 150 years ago.

Since those heady days, when Naples did not just have a king and a court but also riches that are exemplified in its many palaces, the city has come down.

Today, most visitors shun Naples. It was the place where the cholera erupted some years ago. It is the city almost engulfed in rubbish. It epitomises the mafia, a lawless city, where petty theft is rife and poverty dominates.

There may be many interpretations of what led Naples from those riches to today’s poverty. Ours is an interpretation which does not portray itself to be an exhaustive and comprehensive exercise, but is a relevant observation of our present problems with the euro.

Under the Bourbons, Naples had its own currency. With unification, it switched over to the Italian lira. It lost not just its independence as a state, but also the ability to determine its own currency. It also lost the ability to manage its own economy. It became dependent on whatever Rome decided to give it, which, given the prejudices of the north, was not much.

In a way, what happened was almost like what happened when the Berlin Wall came down and the GDR was unified with the DDR. In a unified Germany, the two currencies were united on a 1:1 basis. This was followed up by a huge transfer of (West) German resources, which continues to this day. In Italy’s case, no such thing happened.

We are today seeing the very dramatic effects of the single currency on Greece, Portugal, Ireland, maybe Italy itself.

When the euro was first created, it was said that one of its best points was that there would not be any competitive devaluations among member states.

Some people did warn that if devaluation was not possible (clearly it is not when you form part of one currency), a country in trouble had no means of a corrective adjustment. This warning was not heeded.

The result is Greece. It is Greece’s own fault that it allowed its deficit to grow unchecked, that it bluffed its way into the euro on the strength of fancy accounting, that it allowed a lifestyle of people dependent on government jobs and hand-outs, that it overspent on a bloated Olympic Games event, that it allowed tax revenues to shrink… and so forth.

But as we have seen in the past months, especially in these dramatic weeks, the only sure solution is for Greece to devalue its currency, regain competitiveness and start growing again. But since Greece cannot devalue, it is stuck. The only solution that the other EU member states can offer is austerity and more austerity. Even so, is Greece heading for a default? Maybe it is already defaulting as we write.

The experiences of Naples in one century and of Greece in another are very insightful, although they do not point out how we, the eurozone members, can emerge from the impasse.

With hindsight, we can clearly see there can be no single currency unless the underlying economy is so tightly-meshed that it is a single economy. When ERM and then the euro were created, there was no underlying single economy. That was even more the case when countries such as Greece, which had not made it to the first raft of euro founder members, bent the rules to be allowed in, and the EU consented. Today, we are paying the huge price for such wooliness and lax attention to consequences.

The fact is that this is still a Europe of variable speeds and any attempt to impose a unified currency will not beget a unified economy. On the contrary, as happened in a unified Italy with Naples and as happened in a unified EU with Greece, such shotgun marriages only end up in more bitter tears and hardship.