The United Kingdom has intensified its focus on Russia's clandestine 'shadow fleet' of oil tankers, a critical mechanism Russia employs to circumvent international sanctions imposed in response to its full-scale invasion of Ukraine. This fleet, comprising hundreds of aging vessels with obscured ownership, facilitates the illicit export of Russian oil, generating substantial revenue estimated between $87 billion and $100 billion annually, which directly funds the ongoing conflict in Ukraine.

Despite defence officials vowing 'assertive action' and the UK government receiving legal assurances in early January that such vessels could be detained under the Sanctions and Money Act 2018, numerous sanctioned tankers have continued to transit through the English Channel. BBC Verify tracked 42 sanctioned tankers passing through the Channel after this legal advice was received. Among them was the Sofos, sanctioned by the UK Foreign Office in May 2025, which sailed from Venezuela, loaded oil in Russia in November, and was later seen near St Petersburg. Another vessel, the Nasledie (formerly Blint), also sanctioned in May 2025, is a 20-year-old tanker that became part of the shadow fleet in 2023, changing its name and falsely flying the Comoros flag before switching to a Russian registry. It entered the Channel in January carrying approximately 100,000 tonnes of Urals crude.

Evasion tactics employed by the shadow fleet are sophisticated, including flying under false flags, switching off tracking signals, broadcasting false locations, and even obtaining new IMO numbers, a unique code meant to identify ships for life. The Arcusat (formerly Tia), sanctioned by the US, exemplifies extreme measures, passing through the Channel before being turned around by German federal police and previously obtaining a new IMO number, a move maritime experts deemed almost unheard of.

In response to these activities, the Royal Navy has been actively involved in monitoring and shadowing Russian vessels. Earlier this week, Portsmouth-based patrol ships HMS Mersey and HMS Severn, alongside a Wildcat helicopter from 815 Naval Air Squadron, intercepted the Russian corvette Boikiy and its accompanying oil tanker, MT General Skobelev, as they sailed towards the North Sea. These operations, coordinated with NATO allies, involved close monitoring and data collection. HMS Mersey had previously intercepted other Russian vessels, including the Udaloy-class destroyer Severomorsk and merchant vessels Sparta IV and MYS Zhelaniya, in the North Sea. In the Mediterranean, the Royal Navy Gibraltar Squadron's HMS Dagger tracked the tanker Grinch, one of 544 vessels in Russia's shadow fleet, which was subsequently boarded by French forces with UK support.

Despite the UK's stated commitment and robust monitoring efforts, criticisms have emerged regarding the perceived reluctance to independently seize shadow fleet vessels. Foreign Secretary Yvette Cooper's January announcement about tightening the 'chokehold' on Russia was followed by officials being advised that troops could board and seize tankers. However, while the UK has aided US and French forces in seizures, British troops have yet to independently seize any shadow fleet vessels, even after BBC Verify identified six tankers operating under false flags in the Channel since January. Dame Emily Thornberry, chair of Parliament's Foreign Affairs Select Committee, expressed disappointment, emphasizing the need for robust implementation of sanctions. Liberal Democrat MP Mike Martin questioned the UK's hesitation, highlighting the Royal Marines' capabilities for such operations.

Russia has reacted strongly to the UK's stance. In January, the Times reported a warship escorted the sanctioned tanker General Skobelev through the Channel. Additionally, Russian foreign ministry spokeswoman Maria Zakharova warned that any detention of tankers would be considered a violation of international law. Nevertheless, UK officials, including Minister for the Armed Forces Al Carns MP and Defence Secretary John Healey MP, reaffirmed the government's priority to deter, disrupt, and degrade the Russian shadow fleet, emphasizing continued efforts alongside allies to choke off funds fueling Putin's illegal invasion.