We have a flat in Spain and our tenant paid over 18k backlog of rent on the day of his eviction (we've been trying to evict him for over 9 years) and we are suspicious as to why he didn't declare himself bankrupt rather than risk losing 18k on appeal (which he is very likely to lose).

We think he is sub-letting our flat and was scared that the sub-let tenants would be forcibly evicted and his fraudulent activity found out.

The telephone number we had linked to our flat is no longer operable and he has obviously changed supplier.

Is there an easy way to find out whether he is sub-letting the flat or not? I know we can knock on the door but that means travelling to Spain , etc with no guarantee that anyone would open the door and answer our questions.

Do you think a private investigator might be the answer but how much would that cost?

Any ideas most welcome.