A huge new leak of financial documents has revealed how the powerful and ultra-wealthy, including the Queen's private estate, secretly invest vast amounts of cash in offshore tax havens.
What exactly is offshore finance?
Essentially it's about a place outside of your own nation's regulations to which companies or individuals can reroute money, assets or profits to take advantage of lower taxes.
These jurisdictions are known as tax havens to the layman, or the more stately offshore financial centres (OFCs) to the industry. They are generally stable, secretive and reliable, often small islands but not exclusively so, and can vary on how rigorously they carry out checks on wrongdoing.
The UK is a big player here, not simply because so many of its overseas territories and Crown dependencies are OFCs, but many of the lawyers, accountants and bankers working in the offshore industry are in the City of London.
It's also about the mega-rich. Brooke Harrington, author of Capital Without Borders: Wealth Managers and the One Percent, says offshore finance is not for the 1% but the .001%. Assets of around $500,000 (£380,000) would just not meet the offshore fees the schemes would need, she says.