Delays on Abellio Greater Anglia's first day
Commuters between East Anglia and London faced a series of delays on the first full day of a new operator taking over the running of the region's train services.
Track problems and a broken down train caused disruption to timetables between London and East Anglia.
Network Rail said "points failures" had been reported near London and in Essex.
Dutch train firm Abellio, which took over the Greater Anglia franchise on Sunday, apologised for the delays.
The train broke down in Colchester at about 10:20 GMT.
A company spokeswoman said: "We apologise for the delays and alterations to our services and for any inconvenience this has caused."
Network Rail said its engineers had dealt with points failures near Liverpool Street, in London, by 12:00 GMT and at Manningtree, in Essex, by around 11:00 GMT.
It said the cause of the faults was not thought to be weather-related.
Delays of up to 40 minutes were reported earlier and many services were cancelled, including seven between 15:00 GMT and 17:39 GMT.
Abellio took over the running of the region's trains from National Express East Anglia at 02:00 GMT on Sunday.
Bryan Frost, chairman of the Ipswich and Suffolk Group Campaign for Better Transport, said the issues meant a "very difficult start" for the new operator on its first full day.
"It's very early days for Abellio and I don't think they can be held to account for what has happened today," he said.
"I think today's problems would have happened whatever the company was running the services but it's made for a very difficult start for them.
"These type of failures have happened too often in the past."
In a message posted on its website, Abellio said its internet page was "experiencing problems".
But a company spokeswoman said the site would soon be updated and insisted customers were able to access live train running and timetable information, as well as book and reserve tickets.
For the next 29 months, Abellio will provide train services across Cambridgeshire, Essex, Hertfordshire, Norfolk, Suffolk and links to London.