jonnyg
I'm only guessing, but perhaps it was your
"I'm told the customer was a German (D- reg 109) with too much money!" comment which gave Martin1234 (and now Vizsla) the impression the green eyed monster was about.
"Just how many rules did he break?"
You're the one who suggests it was an 'illegal' - you tell us. What is/are the relevant Spanish law(s)? [Your profile doesn't say if your PPL is UK or Spanish but, as you fly in Mallorca, I assume you can help us with the Spanish rules/regs.]
Based on your experience, what was it about the landing which you consider was dangerous?