Events leading to the announcement of delays

From late 2017, cost pressures escalated, eventually causing costs to exceed the revised £14.8 billion funding agreed by sponsors in 2010.

Risks to the schedule began to materialise. First there were delays to the train software, and then delays to the testing of the trains in the tunnels. Crossrail produced a revised schedule to allow testing while construction and fit out continued, but in August 2018 it was decided that the December 2018 deadline for opening the central section could not be met.