Financial crimes come in all shapes and sizes,
from politicians siphoning off state wealth and officials taking bungs to terrorists buying arms and gangs laundering drug profits.
A common element is the use of shell companies, partnerships or foundations to hide the identities of those moving dirty money.
Such brass-plate entities, whose ownership is typically hard if not impossible to trace,
were at the heart of the theft from 1MDB, a Malaysian state fund, and a $230bn money-rinsing scandal at Danske Bank.
They have been dubbed the "getaway cars" of financial crime.
NGOs such as Global Witness and Transparency International have long highlighted shells' pernicious role,
picking up support from government investigators sick of trails going cold.
Their biggest success was to persuade Britain, in 2016, to become the first G20 country to set up a public register of company owners.
The rest of the European Union is set to follow once a new money-laundering directive takes effect. That leaves plenty of gaps.
But two of the biggest, Britain's offshore territories and America, are also moving in the direction of ditching secrecy
Earlier this month Britain's three Crown Dependencies—Jersey, Guernsey and the Isle of Man—
issued a surprise joint statement pledging to table legislation to introduce public registers by 2023.
They had long insisted that efforts by British MPs to force such a move could trigger a constitutional crisis.
But the growing clout of the transparency movement persuaded them to jump rather than wait to be pushed.
Were three of the biggest offshore financial centres to end secrecy,
it would make it harder for others—including Britain's Caribbean territories,
such as the British Virgin Islands and the Cayman Islands—to keep owners in the shadows.
But campaigners' optimism is tinged with caution.
The Crown Dependencies envisage a staged implementation, with access first for police,
then for financial firms doing due diligence, and only later for everyone else. Some fear a ruse to buy time.