Originally expected to entail an investment of £14.8bn, the project will reduce travel times between key underground stations.
The first trains departed from the new section of the railway, with services having commenced between Paddington and Abbey Wood.
With nine brand new stations in central London, the Elizabeth line services are available every five minutes.
The new railway line will ‘provide new journey options and support wider regeneration and recovery from the pandemic – creating jobs, business opportunities, and a huge economic boost for the country’.
Designed to connect London’s major employment centres, the line is expected to help enhance London’s rail capacity by 10%.
Alstom’s Class 345 Aventra trains operating on the Elizabeth line were constructed in Derby while roundels and signage for the line were delivered by a family-run business on the Isle of Wight.
Under the rolling stock and services provision contract, Alstom will also maintain the trains for the coming 32 years.
The Leeds-based company protected London’s Victorian sewer networks during construction.
London Mayor Sadiq Khan said: “This brand new line is the most significant addition to our transport network in decades. It will add billions to our economy and is set to serve up to 200 million passengers each year.
“I’m sure passengers will enjoy the modern trains, beautiful step-free stations and the reduced journey times across the capital and the South East.”
The Elizabeth line was opened after receiving clearance from the Office of Rail and Road (ORR), the economic and safety watchdog of the UK’s railways.