A man has been arrested on suspicion of collecting information of a kind likely to be useful to a person committing or preparing an act of terrorism.
The 40-year-old man was stopped by police on Wednesday after he arrived into the UK on a flight from Kosovo to Luton airport.
He was investigated by the Met’s Counter Terrorism Command.
Then he was arrested and taken to a local Bedfordshire police station.
The man has since been released on bail to a date in early July.
Officers also carried out a search at a residential property in the Watford area.
All searches are now complete and enquiries are ongoing, Met Police said.