A Russian "shadow fleet" tanker has entered the English Channel for the first time since UK forces boarded the Smyrtos on Sunday morning, ship tracking data shows.
Forwarder, a Russian-flagged ship that left port in Primorsk last week, entered the Channel on Wednesday evening and sailed south. It is broadcasting its final destination as China's Dongying port.
The shadow fleet is formed of hundreds of tankers used by Russia to avoid Western sanctions imposed on its oil exports following the 2022 full-scale invasion of Ukraine.
UK-sanctioned tankers have avoided the Channel since the Smyrtos was intercepted with tracking data showing several vessels altering course to avoid the waterway.
BBC Verify has approached the Ministry of Defence (MoD) for comment. But ship-tracking data appears to show a Royal Navy warship, HMS Tyne, operating in the area near the tanker's location.
Forwarder was sanctioned by the UK, the US and the EU in 2025. Since the British government accused it of smuggling oil from Russia, the vessel has changed its name twice.
Satellite imagery showed Forwarder left Primorsk on 12 June after loading oil. The refinery is the largest in the Baltic Sea and is a critical export hub for Russia's energy industry.
Shadow fleet tankers such as Forwarder have provided a critical lifeline for the Kremlin since the West imposed sanctions on its energy exports.
The clandestine fleet of more than 700 ageing tankers, usually of obscured ownership, is responsible for carrying 75% of Russia's sanctioned oil, according to the MoD.
A Nato official has previously told BBC Verify that the Russian warship, Admiral Grigorovich, has been assigned to escort sanctioned oil tankers. But it is unclear whether the frigate is accompanying the Forwarder.
Admiral Grigorovich was involved in an incident on Tuesday when it fired warning shots towards a British yacht that had apparently moved towards it in the Channel.
A Nato official told BBC Verify that, as of Wednesday evening, Admiral Grigorovich had not moved far from the location of the incident.
In March, UK Prime Minister Sir Keir Starmer announced that British armed forces "are now able to board sanctioned vessels that are passing through our waters" which were not operating in accordance with international law. But experts told BBC Verify it was unlikely the UK or France would seek to intercept the tanker.
"Going after vessels that are falsely flagged or misusing a flag of convenience is one thing, but this would be going after Russia directly which would be a further step up in escalation," said Frederik Van Lokeren, a former Belgian naval officer and maritime analyst.
"Since this is a Russian-flagged vessel, possibly escorted by a Russian warship, I don't expect the UK, or any other Western country, to attempt to board her," Van Lokeren said.
The Smyrtos was boarded and seized by Royal Marines and officers from the National Crime Agency (NCA) as it was sailing without a registered flag in breach of international law. The ship is currently being held by UK officials off the coast of Weymouth and its captain has been charged with contravening sanctions.
Mark Douglas, an analyst with Starboard Maritime Intelligence, also noted that the circumstances surrounding the Smyrtos had provided a much clearer legal basis for the UK to board the vessel.
"Give that the Cameroon registry had delisted Smyrtos before she sailed through the Channel there were definitely reasonable grounds to suspect the vessel was without nationality," he said.
"Forwarder, on the other hand, is flagged by Russia and despite the opaque ownership structure we have no information to suggest that is a false flag."
In the aftermath of the boarding of Smyrtos, ship-tracking data showed multiple sanctioned tankers altered their course to avoid the English Channel. Many sanctioned vessels currently appear to be taking an alternate route around the west coast of Ireland.
In May, BBC Verify established that almost 200 shadow fleet vessels had passed through the English Channel in the months since Sir Keir's announcement that British forces would begin to intercept some sanctioned tankers.
In at least 94 instances, shadow fleet ships briefly crossed into UK territorial waters - a smaller zone that extends up to 12 nautical miles (14 miles; 23km) from the coast.
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