Police were called to Hackney Downs station at around midday today (November 12).
British Transport Police officers arrived and a man in his 20s was arrested on suspicion of obstructing the railways.
Stansted Express, Overground and Greater Anglia Services were impacted.
Trains to and from London Liverpool Street faced 45 minute delays and cancellations.
A BTP spokesperson said: “Officers were called to the line near to Hackney Downs railway station at around 12pm today (12 November) following reports of a trespasser on the tracks.
“Officers attended and a man in his 20s was arrested on suspicion of obstructing the railways.”
