Britain detains sanctioned tanker suspected in Russia's shadow fleet

British forces boarded and detained the sanctioned tanker SMYRTOS in the English Channel, putting one of Russia’s shadow fleet vessels under direct pressure in a six-hour operation. The ship is now set to be moved to an anchorage off the south coast of England, where it will be monitored for environmental and safety concerns as investigators continue their work.

The operation was carried out by Royal Marine Commandos and specially trained officers from the National Crime Agency, with air support from Chinook, Merlin Mk4 and Wildcat helicopters and an RAF P-8 surveillance aircraft. Royal Navy ships HMS Sutherland and HMS Ledbury also backed the mission, which the government said was the first UK-led operation of its kind.

Prime Minister Keir Starmer said he had directed the armed forces to act in the early hours of the morning and said the move delivered "yet another blow to Russia". Defence Secretary Dan Jarvis said the interdiction would help disrupt Russia’s war economy. The Ministry of Defence said the operation was carried out in accordance with domestic and international law and in close coordination with France.

The SMYRTOS case exposes how the shadow fleet works: ageing tankers, opaque ownership structures and weak insurance arrangements are used to keep sanctioned oil moving outside Western restrictions. Britain says the network now numbers more than 700 vessels and carries 75% of Russia’s sanctioned oil, even after the UK has sanctioned more than 500 ships linked to it. That scale makes enforcement difficult, especially when vessels can be renamed, reflagged or shifted through layers of ownership that obscure who ultimately controls them.

Britain is also pointing to pressure already imposed on Moscow’s energy revenues. The government said Russian oil and gas revenues fell by 24% year-on-year in 2025, and later material put Russian oil revenues down 27% since October 2024, to their lowest level since the invasion of Ukraine began. France, Belgium and Finland have recently seized other sanction-busting vessels believed to belong to the same network, suggesting that the SMYRTOS detention is part of a wider European effort to turn maritime enforcement into a more sustained sanctions test case.