Commuters travelling from a major London railway station faced severe disruption after a "serious trespass incident".
Lines into London Euston were shut as emergency services helped someone near Wembley Central station.
British Transport Police said they were called at 16:25 BST and a male had been "taken to a place of safety".
Network Rail warned problems would last until the end of service on Friday as trains were out of place.
Lines later reopened but Network Rail had warned the station concourse remained "very busy" and that crowd management would be put in place.
Power was cut on some trains with one commuter describing how they were stuck on a train.
Ive been stuck on an airless, humid train just north of #Euston for well over an hour. They’ve now had to turn the emergency power off to ensure enough electricity to restart the engines when the time comes. Crew now giving out emergency light sticks. This is ridiculous. pic.twitter.com/zaK4ny28Zm— Emma Dunn (@MrsEmmaDunn) October 25, 2019
London Northwestern Railway, London Overground, Southern and Virgin Trains were all affected:
- Virgin Trains arranged ticket acceptance with other operators and a full list of them can be found here
- Road transport replaced London Northwestern Railway trains between some stations
- London Overground services between London Euston and Watford Junction were delayed by up to 30 minutes
- Southern services, which operate between East Croydon and Milton Keynes Central, were unable to run
National Rail said anybody unable to travel on Friday night could use trains on Saturday for no extra cost.