The findings could bring to an end a two-year mystery that started when drones were spotted flying over four sensitive US military bases in the UK. Investigators believed they were being flown by live operators, but no launch sites were found.
Now, experts at the International Institute for Strategic Studies (IISS), a London-based think tank, have discovered that HAV Dolphin, a Russian-crewed cargo vessel, was docked near Hull at the time. Another vessel, the Seasons 1 tanker, was also in the North Sea near Essex.
Having tracked the HAV Dolphin’s movements, they say it is "highly likely" that Putin waged a drone campaign in Nato airspace across Europe between August 2024 and February 2026, as part of what they say is the "Kremlin’s wider unconventional war on Europe".
The concerted surveillance campaign targeted nuclear sites in the UK, France, Belgium and the Netherlands, the researchers said.