Shadow fleet undeterred as nearly 100 sanctioned ships cross UK

Prime Minister Keir Starmer’s March 25 decision to authorise the UK military to interdict vessels on the sanctions list appears to have had limited immediate effect: a Reuters analysis found that at least 98 Russian vessels subject to UK sanctions transited British waters in the month after the announcement.

Tracking data from LSEG show that 63 of those ships passed within 12 nautical miles of the English coast — primarily via the English Channel — while another 35 moved through Britain’s Exclusive Economic Zone, largely around northern Scotland. Reuters also reported instances of so‑called “spoofing,” where vessels switch off or manipulate tracking signals, and said there was no public record of any of the vessels being boarded or detained in that period.

The vessels are capable of carrying crude oil, grains and other cargoes that can be economically significant; continued unimpeded movement of sanctioned tankers raises questions about supply‑chain risk premia, shipping insurance and freight cost dynamics. The UK government has argued that closing UK waters to these vessels would force operators to take longer, more expensive routes — a factor that could push up logistics and energy costs if deterrence proves effective.

Official UK communications from the Prime Minister’s Office (10 Downing Street) reiterated the intent to interdict shadow‑fleet vessels and noted that some 544 ships are on the UK sanctions list. Analysts cited by Reuters highlight operational and legal constraints — including the absence of a dedicated law‑enforcement coastguard comparable to those in some European neighbours — that complicate widescale interdiction. Meanwhile, several EU partners have mounted their own boarding operations, underscoring the need for coordinated enforcement.

Market participants say the key near‑term variables will be demonstrable follow‑through on interdictions, shifts in insurance and banking policy toward listed vessels, and any persistent rerouting of tankers that raises transport costs. If coordinated seizures and financial choking‑off of facilitators increase, the economic calculus underpinning the shadow fleet would change materially; absent that, shipping risk premia and regional energy security concerns are likely to remain elevated.