To Malta, the whole island is a single mafia. Cosa nostra can do business. But they don't control the Maltese.
Historical, maltese criminals are strong involved in different racketeering in London. But there are still supposed to be boys from them today
Maltese crime in London is dead and buried. Historically they were mostly involved in running brothels in Soho. Up until the 1960's - 1970's that was a thing. There were still Maltese operating in brothels in the 1980's, but the last remnants were wiped out when the Canning Town group took over by force. This was actually in the news in the late 90's;
https://www.theguardian.com/uk/1999/nov/28/tonythompson.theobserver As for the existence of a "Maltese mafia" on the island itself. I've no doubt it exist in some form, but it's not a major force on a European scale.
