Petr Aven, a Russian oligarch with a mammoth art collection, has violated international sanctions with his habit of buying and flipping luxury cars, the National Crime Agency alleges. The agency has frozen two bank accounts utilized by Aven, saying that he used the corporate accounts to bankroll cover-ups of car purchases and send a £200,000 payment to two car dealers. In February, the European Union sanctioned Aven, referring to him as one of Vladimir Putin’s “closest oligarchs” and a person who “actively supported materially or financially and benefited from Russian decision-makers responsible for the annexation of Crimea and the destabilization of Ukraine.”