Subsequently it became one of the most economically dynamic communities in Spain and its capital, Barcelona, one of the most visited by tourists of all European cities and the 12th most popular in the world. There were 18 million visitors to Catalonia in 2016, as many as there were international visitors to the whole of Canada.
This action, employing unprecedented constitutional powers and referred to in the media as 'the nuclear option', follows the "illegal" independence referendum held on 01-Oct-2017. Various polls held over the last decade indicated that over 90% of the regional population preferred Catalonia's transformation into an independent State and despite attempts to prevent the referendum taking place that was the declared result, albeit on a low turnout prompted by several factors.
Regional government officials have vowed to resist the takeover and the imposition of elections, which is being described as a 'coup d'état' by Spain, to which the Spanish government retorted by threatening to "discipline them", prompting a declaration by one political party that Catalan citizens should engage in "massive civil disobedience". The war of words multiplies with each passing day and with 0.5 million people - and potentially one million or more - frequently taking to the streets of Barcelona to protest, the prospect of matters suddenly escalating out of control is as ripe as it is in the case of the North Korean missile crisis.
The remainder of Spain is split over Catalonian independence (as are the Catalans themselves) though it is safe to say that as the referendum demonstrated the vast majority of Catalans favour it while a slightly smaller majority of Spaniards elsewhere are against it.
If and when direct rule is imposed, and especially so if and when Catalonia actually declares independence, events are unlikely to remain limited to Catalonia and Madrid. There are independence movements in several of Spain's other autonomous regions, such as parts of Valencia (which includes the Costa Blanca, Alicante and Benidorm, Europe's largest resort), the Balearic Islands (Mallorca, Menorca, Ibiza and Formentera), Andalusia (Malaga and the Costa del Sol) and Galicia in the northwest, where unification with Portugal is sought by some.
While there is no suggestion yet that it will do so, the Basque separatist movement could also be rejuvenated. The armed wing, ETA, which killed over 800 people during its almost six-decade long fight for independence, finally laid down its arms as recently as 07-Apr-2017.
The nightmare scenario, as unlikely as it may seem just yet, is of a return to civil war. The Spanish Civil War (1936-1939) out of which the Dictator, General Francisco Franco, emerged as leader for almost 40 years, killed half a million people while another half million fled the country. It began as a result of the refusal of army officers to accept the jurisdiction of a government, something the army may very soon be asked to do again. Just as in Sarajevo in 1914, so much as an attempted assassination of a leading political figure on any side could ignite a powder keg.
The European Union will not intervene. It has said it will not do, and it has more than enough on its plate with 'Brexit', hardening attitudes in many countries in Eastern Europe and the fact that there are breakaway movements in many EU states. The separatist SNP (Scotland), Plaid Cymru (Wales) and Sinn Féin (Ireland) all sent observers to the referendum.
So far there has been a smallish but noticeable impact on tourism, most of it prompted by the regular demonstrations that are televised worldwide and by the brutality of the police when they attempted to halt the referendum, reportedly hospitalising over 800 people and which was universally condemned by foreign politicians. It is noticeable particularly because there was only a very small negative tourist reaction to the terrorist attack which took place in Barcelona and Cambrils on 17-Aug-2017.
CHART - The United Kingdom, France and Germany are the largest source markets for international visitors to Spain
Source: CAPA - Centre for Aviation, Spain's Ministry for Industry, Energy and Tourism and Instituto Nacional de Estadistica
In the first two weeks following the referendum both foreign tourist and air travel bookings to Catalonia slumped by 15-20%, equivalent to over EUR1 billion in revenues. Some vacation trips have been redirected from Barcelona to Madrid. In some ways, that might be a blessing in disguise, at least in the short term. Barcelona was wilting under the weight of more tourists than it could handle in the high season. On the other hand there are 400,000 people working in the Catalonian tourism industry and a 20-30% reduction in tourist numbers is anticipated by the Spanish tourist industry to the end of the year even under the impasse that exists now.
CHART - Across the first eight months of 2017 tourism arrivals into Spain were up 9.3% on last year, the second fastest annual rate of growth in the 2010s
Source: CAPA - Centre for Aviation, Spain's Ministry for Industry, Energy and Tourism and Instituto Nacional de Estadistica
There are other potential losers. Expats (there are still 300,000 from the UK alone) may decide that now is the time to return home. That would be a one-off fillip for the airlines but a permanent loss thereafter as both their travel and those of their friends and relatives ends. Many domestic and international airlines are heavily committed to operations in and out of Spain. And the international airlines have few other options apart from Portugal as North African, Turkish and Egyptian resorts are still considered off-limits in many cases owing to the terrorist threat.
Tourism is responsible for 14% of Spain's GDP and has helped the economy recovery from over five years of recession, with growth of 3.2% in each of the last two years. That had already been revised down to 2.8% and further reductions are anticipated. They could be big reductions.
CHART - Barcelona El Prat Airport has a significant exposure to foreign airlines as schedule data for the week commencing 23-Oct-2017 illustrates
Source: CAPA - Centre for Aviation and OAG
Many commercial organisations have threatened to leave Barcelona and the wider province and some have done so already, which impact on business travel.
Then there is the impact on AENA's smaller airports, which its partial privatisation, and the legal decree that permitted it, was supposed to protect. In the event that tourism collapses resources would inevitably be pumped into propping up the major airports first. AENA's traffic figures for October, which will probably be published in the first or second week of November, are awaited with great interest.