Network Rail carried out major track replacement work at Colchester and between Liverpool Street and Bethnal Green over the Christmas period.
The work caused some disruptions for holiday travellers - but bosses at the company said it should ensure trains could travel more reliably over the next few years.
Mark Budden, Network Rail Anglia Route Director, said: "Over the Christmas and New Year period hundreds of our railway staff carried out crucial improvements and upgrades to the Anglia rail network.
"We took great care to keep the disruption to a minimum though, inevitably, some train services were affected so I'd like to thank our passengers for their patience and understanding while we carried out the works.
"We will continue to improve the network in 2020 and work in partnership with train operators to deliver a better service for passengers and freight users."
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