Trains were delayed this evening due to a trespasser at Harrow and Wealdstone station.
London Midland and Virgin Trains services between London Euston and Birmingham New Street and Milton Keynes Central stations were held up by up to 40 minutes as a result of the incident at around 6.20pm.
The incident has also affected Southern Trains services.
Lines have since reopened but delays are still likely.
Virgin Trains has advised a normal service is not expected to resume until 7pm.