U.K.-registered companies are popular tools in money laundering and tax evasion schemes, including ones used by people in Ukraine. So is London real estate. And multiple commentators have dubbed London the money laundering capital of the world.

In the past few years the U.K. has introduced multiple pieces of legislation to fight against the flow of so-called dark money through its economy. However, lawmakers and experts have recently identified enforcement weaknesses that might let sophisticated operators slip through the cracks. New transparency rules in Britain’s overseas territories have also run into delays.