"Officers from the Met's Counter Terrorism Command have today, Nov. 14, arrested a man on suspicion of terrorism offences," a statement from the Metropolitan Police said.
The man was arrested "after arriving at Heathrow airport on an inbound flight to the U.K. from Turkey," and "the arrest is Syria-related," according to the statement.
The man was arrested on "suspicion of preparation of terrorist acts" and he will remain in police custody, it said. Further details were not disclosed.
Earlier, Turkey had said it was deporting a U.K. citizen who was under their custody for being a member of terrorist organization Daesh.
The legal process continues to repatriate foreign terrorists to their home countries, Turkey's Interior Ministry said Thursday.
A foreign terrorist fighter of British nationality was sent back to London, while seven from Germany were sent to Berlin, according to a ministry statement.