They are kept that way by the constitution, which separates police officers from other public servants, meaning they do not qualify for the standard minimum wage and the 40-hour weekly work limit.

ECONOMIST: Organised crime in Mexico

While those are the only countries in the world selling citizenship directly, in the Dominican Republic, foreigners who invest in real estate or local businesses can obtain citizenship after a minimum residency of just six months (as opposed to the standard two years that other people would have to wait).

BBC: The equation of dual citizenship

The WHQS sets a minimum standard for homes, with certain requirements at its core that are more challenging than similar schemes in other parts of the United Kingdom.

BBC: Public Accounts Committee