Look, I know I'm a Rossi supporter but I'm also a tax specialist. I know when a client comes to me with international tax issues, they most the time don't have a clue themself. If you think I'm crapping on about this, tell me what you think.
I'm a sports person who's made a lot of money. A country (the UK) I play sport in and enjoy spending time in has a law which says that if you are an ex-patriate who travels to that country (the UK), takes up residence in (but is not a citizen), then I don't pay tax on my earnings from foreign sources that are not remitted (paid) into the UK. This is the UK law as it stands and I have clients on millions who are in this situation coming from Australia. Italy will have its own tax residency laws. So will the UK. There will also be a double tax agreement between the two which allocates tax residency status where a person is deemed to be a resident of both countries under their respective domestic laws.
The only people that know the technicalities of this situation are the tax advisors involved. The client understands what the tax advisors tell them.
Under the double tax treaty between italy and the UK tax residency status is allocated under Article 4 to firstly the place in which the person has a home... if they have a home in both countries, to the place where they have closer economic and personal relations. Obviously Italy would be most likely to be the place where Valentino has the closer ties. Normally when someone wants to change tax residence, you go through these things. They need to buy a house in the UK, they need to sell their home in their home country (but not compulsory), they need to ensure there are strong economic ties with the location they are at and break those with their old country. A lot of countries also have a >183 days test which says that providing they are not in the country for 183 days they are not a resident - this ties back to the references in the news articles by Valentino that he believed he was out of the country for 7 months in the year so he had no problem.
The international tax space is very complicated and only the advisor would know how much risk there was in the advice they provided. Valentino wouldn't know this. This area of law gets tested regularly because people just don't know. My thoughts are that he would have moved to the UK because he understood that it was tax advantageous to him. He would have spent the majority of his time there. He would also have maintained a home in Italy and stayed there when in the country, including the couple of races there. He was out of the country more than 183 days, but he would have maintained economic and personal ties there - being in the public eye, his personal ties are easy to identify. His economic ties are traceable. This is a judgement call that tax advisors all over the world get paid thousands of dollars to decide. To protect their own arses, their practice is to advise the client what they need to show to shift their tax residence from one country to another however they generally don't advise this in retrospect, they also don't generally double and triple check to ensure that the client is doing what they said. The issue is that a client will miss the nuances of the different points that they need to tick off and the effect that a failure to tick a point off will have.
The celebrity clients I deal with have no idea about tax - think about it - not many have uni degrees and tax experience when they end up in the public eye at a young age. These clients rely on their manager to put them in touch with the right accountant and solicitor. That's what they pay the 10-20% for, among other things. Although it is possible that Valentino did know that something was wrong, it was 90% likely that he didn't.