Do sanctions ever stop grand corruption and human rights abuses? The question is worth asking as Britain slaps asset freezes and travel bans on Zimbabwe's top securocrats – a spy chief and a police chief, and commander of the presidential guard – all of whom it blames for the deadly crackdown on dissidents and continuing theft of state property.

Measures such as the Magnitsky Act in the United States and its counterpart in Europe seem to do little to rein in their targets. Over a decade ago, Britain froze an account in Balham with US$30 million in it linked to Zimbabwe's President Emmerson Mnangagwa, when he was still one of Robert Mugabe lieutenants. Nothing changed. The US has sanctioned Mnangagwa's ally, Kudakwashe Tagwirei, whose commercial ambitions, we report this week, are getting ever more grandiose.

US sanctions against Israeli magnate Dan Gertler for graft in Congo-Kinshasa were onerous enough for him to lobby outgoing President Donald Trump for a reprieve. Five days before Trump left office, Gertler got a special licence suspending the sanctions for year. That has triggered calls to new Treasury Secretary Janet Yellen to cancel the licence.

A recurrent problem with sanctions is the lack of deterrent against the facilitators of much of the grand corruption – the Western-based accountants, auditors and lawyers who help run enterprises whose beneficiaries they know to be criminals.