"The central section will be substantially complete by the end of the first quarter in 2020, except for Bond Street and Whitechapel stations where work will continue".
"Mark Wild, Chief Executive of Crossrail Ltd., now expects the line to be running ".as soon as practically possible in 2021".
A future Elizabeth line train at Old Oak Common. The bulk of the delay this time is being blamed on the "software development for the signalling and train systems" and safety approvals processes, although the positive news is that test runs running over the full line should start in 2020, so it will happen at some point and is not going to be revoked, backfilled and forgotten about.
Transport for London said a more exact timetable will be unveiled "early in 2020".
The latest projections now show a central cost forecast (including risk contingency) of approximately £15,363m, which is £400 million more than the funding committed under the exisiting Financing Package.
Track, tunnels and new trains were completed in 2018, but stations and safety systems remain problematic. The total cost of Crossrail was previously estimated at £17.6bn but the latest overrun means the cost of the project has risen to as much as £18.25bn from an initial budget of £15bn.
Mr Wild said he wants to "ensure reliability of the railway from day one of passenger service".
Transport for London said on Friday it had now been notified that the line would not open until 2021.
He added: "We are doing everything we can to complete the Elizabeth line as quickly as we can but there are no short-cuts to delivering this hugely complex railway".
While the core section - passing through places like Paddington, Bond Street and Liverpool Street - is the most high-profile part of the Elizabeth line, it is not the only component. "Further modelling scenarios" suggest higher levels of risk to the project that would cost an extra £650m, TfL said.
"The delay creates huge issues for many businesses that have made investment decisions based on its original opening date of December 2018".