Transport for London (TfL) attributes the delay to the complex nature of integrating the modern fleet with the 120-year-old Tube network, citing engineering challenges.
The new trains will offer significant upgrades, including 10 per cent more capacity, wider double doorways, air conditioning, real-time digital displays, and onboard CCTV.
These state-of-the-art trains are designed to be lighter and more energy-efficient, consuming 20 per cent less energy than existing models.
TfL's Chief Capital Officer, Stuart Harvey, expressed regret over the delay but emphasized the critical need to ensure safety and top condition before the trains begin service.