London’s much delayed Crossrail transit project is due to start service May 24 when the tunneled section through the city opens. The new Elizabeth Line operated by Transport for London will have limited service until fall while testing continues. The central Bond Street station is tentatively scheduled to open later this year.

"We are using these final few weeks to continue to build up reliability on the railway and get the Elizabeth line ready to welcome customers," said Andy Byford, Transport for London Commissioner. "We look forward to showcasing a simply stunning addition to our network.”

However, getting to this point has been an epic struggle. The line, which links communities east and west of the capital with 42 km of tunnels and ten new stations under London, was originally due to open in December 2018, according to the National Audit Office.

Last July the auditors put the program's cost at $23.6 billion. Crossrail’s budget was set at $20 billion when the government approved the start of construction in 2007. A period of value engineering in 2010 reduced that figure to $18.5 billion, partly reached by pushing back completion to December 2019. 

Overruns occurred largely because the project company Crossrail Ltd., Transport for London, Dept. for Transport and contractors had not "appreciated how complex it would be to bring together all of the separate systems and assets required and assure them as safe and working, or how long it would take," said the auditors.