I don't understand why this is such a big deal. The solution is right there in the article - send a few ships from the navy, like the Spanish treasure fleets of old.
If England doesn't want armed Venezuelan ships in their waters, use a freighter and escort it all the way back. Divide up the cargo between the ships if you're really paranoid.
The author is inventing a problem where none exists. Transporting large amounts of heavy cargo overseas is a solved problem.
Ordinarily, you'd want insurance on such a shipment. Even if you sent the navy, getting insurance for the transport between the bank vault and the armed ships could be an issue.
If England doesn't want armed Venezuelan ships in their waters, use a freighter and escort it all the way back. Divide up the cargo between the ships if you're really paranoid.
The author is inventing a problem where none exists. Transporting large amounts of heavy cargo overseas is a solved problem.