LONDON (Reuters) – London’s new flagship railway Crossrail cannot say when the much-delayed line will open, or what the final cost will be, Britain’s spending watchdog said on Friday after Europe’s most ambitious infrastructure program hit the buffers.

FILE PHOTO: Crossrail workers are seen in the new Farringdon underground station of the Elizabeth line which had been expected to open in December 2018, in London, Britain June 15, 2018. REUTERS/Peter Nicholls/File Photo

Due to open in December 2018, the rail line running between Heathrow Airport to the Canary Wharf financial district via central London, is now unlikely to open before 2021 after it was hit by testing and signaling problems.

The National Audit Office (NAO) said on Friday the mismanagement of Britain’s most important infrastructure project