A private jet has been impounded at Farnborough Airport in Hampshire as authorities investigate its connection with a billionaire Russian oligarch.
The jet flew into the country last Thursday and UK officials believe oil tycoon Eugene Shvidler was on board.
They are now investigating whether the plane is permanently leased to Mr Shvidler and falls under UK sanctions.
The Luxembourg-registered jet was due to take off from the UK to Dubai, but officials have now prevented this.
It comes as the UK announced new sanctions on Russian aircraft.
Ministers are making it a criminal offence for planes owned or chartered by Russians to enter UK airspace, and new trade sanctions will prevent all UK exports of aviation or space-related technology to Russia.
Mr Shvidler has himself not been personally sanctioned by the UK at any stage.
Announcing the new measures, Foreign Secretary Liz Truss said the changes would inflict further “economic pain on Russia and those close to the Kremlin”.
She added the government would continue to support Ukraine and “work to isolate Russia on the international stage”.
Transport Secretary Grant Shapps said the UK was “one of the first countries to ban Russian aircraft and today we are going even further by making it a criminal offence for Russian aircraft to operate in UK airspace”.
“We will always work to deny [Russian President Vladimir] Putin and his cronies the right to continue as normal while innocent Ukrainians suffer.”
Nick Watt, political editor of BBC Two’s Newsnight, said the measures would address the “grey area” of private jets that are registered in a third country being chartered by wealthy Russians.
Sources told Newsnight that identifying a plane as Russian is not just a matter of following it on a radar, but about “detective work” to establish its true origins.
The new sanctions come shortly after the UK government confirmed it would introduce a ban on all Russian oil by the end of the year, with a similar move announced by the US..