Dozens of Russian oil tankers sanctioned by the UK have sailed through the English Channel this month, ignoring the UK’s promise of "assertive action". These tankers are part of a shadow fleet used by Russia to dodge sanctions on its oil after its invasion of Ukraine. The UK government received legal clearance earlier this month to detain these vessels. However, 42 sanctioned tankers, including the Sofos and the Nasledie, moved through the Channel even after this advice. The Sofos, sanctioned in May 2025, sailed from Venezuela and is now near St Petersburg. It loaded oil in Russia in mid-November and later switched off its tracking while in Venezuela. The Nasledie, over 20 years old and renamed from Blint in November, entered the Channel in January carrying 100,000 tonnes of Russia’s Urals crude. Shadow fleet ships often change flags and turn off tracking to avoid detection. UK Foreign Secretary Yvette Cooper said the government is ready to "tighten the chokehold" on Russia with more "assertive actions". British troops helped seize tankers with U.S. and French forces but have yet to board any shadow fleet vessels independently. Experts say these ships, sailing under false flags, can be seized as stateless vessels. MPs like Dame Emily Thornberry express disappointment at the lack of interceptions, calling for strong sanction enforcement. Russia responded by escorting tankers through the Channel and warned that any seizure would harm its interests. The UK Ministry of Defence said disrupting the shadow fleet is a top priority and efforts will increase. Other tankers sanctioned by the U.S. and EU but not the UK also passed the Channel, using tactics like changing identities and switching off signals. Analysts estimate the shadow fleet moves $87 billion to $100 billion worth of Russian oil yearly. In December 2025, 68% of Russian crude oil was transported on sanctioned tankers. Critics say the shadow fleet helps fund Russia’s war in Ukraine and stresses the need to cut off this economic lifeline to end the conflict.