When asked the cause of the delay, Crossrail said: “The original programme for testing has been compressed by more time being needed by contractors to complete fit-out activity in the central tunnels and the development of railway systems software. Testing has started but further time is required to complete the full range of integrated tests.”

On the current state of works, it added: “Construction activity is drawing to a close with the completion of the remaining mechanical, electrical and communications systems along with architectural fit-out in the new central section stations. The remaining rail infrastructure works will complete this year. This ranges from removal of temporary services to completing the remaining installation of the permanent lighting and drainage pumps in the tunnels.”

Simon Wright, Crossrail chief executive said: “The Elizabeth line is one of the most complex and challenging infrastructure projects ever undertaken in the UK and is now in its final stages. We have made huge progress with the delivery of this incredible project but we need further time to complete the testing of the new railway. We are working around the clock with our supply chain and Transport for London to complete and commission the Elizabeth line.”