Published by Global Banking & Finance Review®
Posted on March 31, 2026
4 min readLast updated: March 31, 2026
Add as preferred source on GoogleSince March 2026 UK announced authority to detain Russian ‘shadow fleet’ tankers, at least 25 sanctioned vessels have still transited through UK waters—indicating the measure has yet to significantly deter such movements.
By Andrew MacAskill and Muvija M
LONDON, March 31 (Reuters) - More than two dozen ships sanctioned for being part of Russia's so-called shadow fleet have passed through UK waters since Prime Minister Keir Starmer last week authorised the military to detain vessels used by Moscow to export oil.
The figures based on ship tracking data analysed by Reuters show that oil tankers sanctioned by Britain are continuing to travel along England's southern coast in the same numbers as before the announcement.
British officials said almost a week ago that the military was preparing to board the vessels for breaches of sanctions and the government hoped the announcement would force the ships to take longer routes away from British waters. Russia called it a "deeply hostile move" and said it could retaliate.
Since that statement, the British military has not announced it has boarded any Russian vessels while at least 25 sanctioned ships have entered British waters when travelling through the Channel as before, according to the Reuters analysis.
STARMER SAYS RUSSIA COULD PROFIT FROM OIL PRICE RISE
James Fennell, a former British naval officer, said the British military would probably target Russian vessels only selectively, citing the complexity of an operation, the threat of legal challenges and the risk that such action could bring Britain "one step closer to war with Russia".
"The government is hoping the threat acts as a deterrent and will gauge the effect before sanctioning a potentially risky boarding operation," he said. "They will be using back channels to tell Russia to cease and desist."
Britain's Ministry of Defence said any enforcement action would be "considered on a case-by-case basis" and it would not provide "a running commentary" on potential action.
Starmer said last Wednesday evening he had authorised the boarding and detention of Russian vessels to prevent Russian President Vladimir Putin from making "dirty profits" from the sharp rise in oil prices driven by the U.S.-Israeli war with Iran.
Russian ships in the so-called shadow fleet of tankers used by Moscow to fund its four-year war against Ukraine sail through the Channel as it is the most convenient route for travelling between the Baltic and southern Europe and beyond.
Other European nations, including France, Belgium and Sweden, have in recent months boarded and detained vessels to disrupt the network of ships.
Trump this month temporarily eased sanctions on Russian oil as part of his administration's attempt to tame energy prices.
'VERY LIMITED' LEGAL GROUND TO BOARD SHIPS
Britain has placed sanctions on 544 Russian shadow fleet vessels, meaning they are prohibited from entering British ports and can be detained, according to the government.
Pole Star Global, a maritime data and intelligence company, said about two dozen of these ships travelled through British waters a week on average since the start of the year.
Douglas Guilfoyle, a professor who specialises in maritime security at the University of New South Wales, said even though Britain had sanctions on Russian vessels it would need to rely on untested legal arguments to board the ships.
Guilfoyle said that there were only two clear legal bases to detain the vessels: a U.N. Security Council sanctions regime - not in place at present - or treating seizures as a "countermeasure" in response to Russia's war in Ukraine, which he described as a "novel and untested" legal argument.
"There are very limited exceptions that would justify interference with the right of transit passage or the right of innocent passage by a foreign vessel – even one subject to UK autonomous sanctions," he said.
Brett Erickson, a sanctions expert who works at the consulting firm Obsidian Risk Advisors, said the British government looked weak because it announced it was ready to detain Russian vessels, but had yet to take any action.
"With sanctions you can't be half in, you either have to be all in, or all out," he said.
(Editing by Alison Williams)
At least 25 sanctioned Russian vessels have passed through UK waters since the British government's recent threat to board such ships.
The UK authorized military action to deter Russia from profiting from rising oil prices caused by global conflicts, specifically targeting ships used for oil exports.
As of the article's publication, the British military has not carried out any publicized boardings of Russian vessels.
Legal experts say boarding requires novel and untested legal arguments, and there are limited exceptions in international law to interfere with transit or innocent passage.
Countries like France, Belgium, and Sweden have boarded and detained Russian vessels to disrupt the shadow fleet network.
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