Thousands of commuters were left stranded or facing lengthy delays as the Elizabeth line was brought to a standstill on Tuesday.
Trains were unable to run on the Elizabeth line between London Paddington and Stratford, as well as to Abbey Wood, after a large spillage of hydraulic fluid on the track.
The issue is expected to cause major disruption until 7pm, National Rail said.
Elizabeth line services were unable to stop at central London stations including Bond Street, Tottenham Court Road, Farringdon and Whitechapel, as the liquid was cleaned up.
As of Tuesday evening, all lines had officially reopened, with some lingering disruption, as passengers were warned to expect delays.
But the Elizabeth Line remained suspended between Whitechapel and Stratford in east London over a separate track fault at Stratford. The issue also hit Greater Anglia services.
Several delays and suspensions on the Tube network caused headaches for commuters travelling home on Tuesday.
There was no service between Turnham Green and Richmond on the District line due to a Network Rail points failure at Gunnersbury, and delays between Earl's Court and Wimbledon.
On the London Overground there was no service between Willesden Junction and Clapham Junction, and severe delays between Richmond and Stratford while Network Rail fix a track fault at Willesden Junction.
There was no service between Hackney Downs and Chingford due to ongoing planned engineering work. Delays also hit the DLR and Central line on Tuesday evening.
Transport for London (TfL) told the Standard the Elizabeth line issue started when a maintenance train leaked the fluid on a section of track in central London.
TfL had earlier said that late engineering works had prevented trains from running on the Elizabeth line on Tuesday.
Earlier Tuesday, services between Paddington and Shenfield were cancelled or revised to run between London Liverpool Street and Shenfield.
Services between Paddington and Abbey Wood were all cancelled due to the issue.
TfL warned that trains running on the line between Paddington and Heathrow, as well as on the branch to Reading, were also hit by severe delays.
The London Underground network was also hit by major issues on Tuesday morning after a points failure at Edgware Road halted trains on the Circle and District Lines.
The points failure also caused severe delays on the Hammersmith & City Line.
Passengers described a “day of misery” as they were hit by long delays when trying to cross the capital.
One commuter wrote on X: “Total mess at London underground this morning, could't get to east London from Paddington on time. Elizabeth line cancelled, circle line delayed, had to change multiple trains to reach office.”Another person complained: “How is it that two years after the Elizabeth line started working, it’s just as much a disorganised mess as it originally was.”
A third traveller added: “I swear every time I use the Elizabeth line there’s something wrong with it”
A TfL spokesperson said: “We apologise to Elizabeth line customers for the disruption to their journeys this morning. This was caused by a fault with an engineering train overnight.
“We are working as quickly as possible to restore a normal service.”
