The former head of a crime syndicate told Japanese magazine Shunkan Gendai that his organisation used the cards to transport stolen money abroad, according to a translation published by IGN.

The cards can be extraordinarily valuable – with the record for a single card currently sitting at $5 million (c. £3.96m) – and are small and easy to transport in large quantities, he said.

He also revealed that crime syndicates were using the same techniques as hobbyist collectors to find the most valuable cards, for example using metal detectors to find booster packs with more valuable foil-wrapped “shiny” cards.

The interview could shine new light on the arrest earlier this year of a Japanese yakuza boss who was found with more than two dozen Pokémon cards.