In March 2007, authorities raided the home of Zhenli Ye Gon, a pharmaceuticals magnate based in Mexico City. At his house in the plush suburb of Lomas de Chapultepec, they found $205.6m in hundred dollar bills. The piles of notes were so large they spilled out of the lounge, down the corridors and into the kitchen.

While the raid was going on, Mr Ye Gon was reportedly spotted in Las Vegas indulging in his favourite hobby: high-stakes poker. Now in a US prison awaiting extradition to Mexico, he stands accused of buying from China and then selling to drug gangs the precursor chemicals used to make methamphetamine, a stimulant known in north America as “crystal meth”. As it happens, Mr Ye Gon was also a long-time client of banking giant HSBC.

The episode, contained in a report this week from the US Senate, shows what American lawmakers have called a systemic failure by the UK’s largest bank to control money laundering in its global operations and stop such funds from entering the US.