Not much is known about Viktor Artemov, the Switzerland-based Ukrainian who landed on the US government’s blacklist earlier this month after allegedly using a fleet of 11 tankers to ship hundreds of thousands of barrels of Iranian oil.

But a review of shipping databases, broker reports and corporate registry data carried out by TradeWinds shows Artemov was able to use recently registered companies to acquire much of his fleet, worth more than $260m, in just four months last year.