Delays in train procurement risk pushing back the start of the Crossrail service.

This is according to the National Audit Office (NAO), which has published a report into the ambitious project. 

Delays have been caused by transport officials changing their approach on how the new trains will be procured. It was initially decided that vehicles should be purchased via the private sector but it has now been agreed that deals would be completed through public companies. The Department for Transport has already contributed £100 million to the project.

The report stated: "The late decision to change funding of the rolling stock introduced a new delivery risk, but this is now being managed." It warned that bosses must meet the April deadline to procure the trains to avoid delaying the service.

The Crossrail project will build new railway networks between central London and the south-east, and is currently halfway through construction. The NAO estimates that the service will not be operational for another six years.