A man has been arrested on suspicion of trespassing at Shoreham railway station and possessing a Class A drug, British Transport Police said.
British Transport Police received reports of a person trespassing at Shoreham railway station at 5.40am yesterday morning, a spokesman said.
The suspect then boarded a London-bound train and officers were deployed to intercept the service, the spokesman said.
A 37-year-old man was arrested on suspicion of trespassing and possession of a Class A drug when the train reached Gatwick Airport, confirmed the spokesman.
Anyone who witnessed the incident is asked to contact British Transport Police by texting 61016 or calling 0800 40 50 40 and quoting reference 47 of 30/10/18.