The main feature of the project was the construction of a new railway line that runs underground from Paddington Station to a junction near Whitechapel.

The concept of large-diameter tunnels crossing central London to connect Paddington in the west and Liverpool Street in the east was first proposed by railwayman George Dow in The Star newspaper in June 1941.

Like SuperCrossRail, Superlink envisaged linking a number of regional stations via a tunnel through London, but advocated the route already safeguarded for Crossrail.

[23] The threat of diseases being released by work on the project was raised by Lord James of Blackheath at the passing of the Crossrail Bill.

He told the House of Lords select committee that 682 victims of anthrax had been brought into Smithfield in Farringdon with some contaminated meat in 1520 and then buried in the area.

[24] On 24 June 2009 it was reported that no traces of anthrax or bubonic plague had been found on human bone fragments discovered during tunnelling.

[29] By September 2009, preparatory work for the £1 billion developments at Tottenham Court Road station had begun, with buildings (including the Astoria Theatre) being compulsorily purchased and demolished.

[35] A subsequent London Assembly report was highly critical of the insensitive way in which Crossrail had dealt with compulsory purchases and the lack of assistance given to the people and businesses affected.

[48] The south east section of the infrastructure was energised in February 2018, with the first test train run between Plumstead and Abbey Wood that month.

[49] In May 2018 the overhead lines were powered up between Westbourne Park and Stepney, the installation of platform doors was completed,[50] and video was released of the first trains travelling through the tunnels.

[56] Crossrail said major challenges before completion included writing and testing the software that would integrate the train with three different track signalling systems, and installing equipment inside the tunnels.

[69] Three construction workers died from suspected heart attacks over six months in 2019, but Crossrail announced that, following extensive testing, the air quality at Bond Street station was within acceptable limits.

It was revealed that an industrial relations manager, Ron Barron, employed by Bechtel, had routinely cross-checked job applicants against the Consulting Association database.

[71] In May 2012, a BFK manager challenged their subcontractor, Electrical Installations Services Ltd. (EIS), saying that one of their electricians was a trade union activist.

[citation needed] The Scottish Affairs Select Committee called on the UK Business Secretary, Vince Cable, to set up a government investigation into blacklisting at Crossrail.

Electrician Daniel Collins had raised health and safety concerns at the Bond Street station site in February 2015, was fired three days later, and faced repeated difficulties in gaining new employment on the project.

Crossrail and the contractors denied all Collins' allegations, saying they settled the court case "for purely commercial reasons" and "without admission of liability or wrongdoing".

Over 100 archaeologists have found tens of thousands of items from 40 sites, spanning 55 million years of London's history and prehistory.

[86] Delays to the project of several months were caused by the COVID-19 pandemic in England,[87][88] and in late 2020 this reduced the number of workers that could be safely on-site.

From Sunday 6 November trains began running directly from Reading and Heathrow in the west to Abbey Wood, and from Shenfield in the east through to Paddington as the surface railways connect with the central tunnels.

[98] Various commentators advocated an extension further west as far as Reading because it was seen as complementary to the Great Western Electrification project which was announced in July 2009.

[101][102][103] A flyover at Airport Junction near Hayes & Harlington station allows Heathrow Express trains to pass over the track used by Crossrail, avoiding delays caused by crossings.

[110][111] The Elizabeth line logo features a Transport for London roundel with a purple ring and TfL-blue bar with white text.

The Custom House to North Woolwich section, included a £50 million investment to renovate and reuse the Connaught tunnel.

[119] It was planned to bring at least one mock-up to London for the public to view the design and give feedback before final construction commenced.

[136] In May 2019, the chief development officer confirmed discussions are ongoing about a station for the airport as part of the proposed extension to Ebbsfleet.

[144][145] However, prior to the submission of the Crossrail Hybrid Bill to Parliament in 2005, the branch was truncated at Abbey Wood to cut overall project costs.

[151] The Mayor's Transport Strategy estimated that an extension could assist in delivering 55,000 new homes and 50,000 new jobs planned along the route in Bexley and north Kent.

[156] In August 2014, a statement by transport secretary Patrick McLoughlin indicated that the government was actively evaluating the extension of Crossrail as far as Tring and Milton Keynes Central, with potential Crossrail stops at Wembley Central, Harrow & Wealdstone, Bushey, Watford Junction, Kings Langley, Apsley, Hemel Hempstead, Berkhamsted, Tring, Cheddington, Leighton Buzzard and Bletchley.

This extension would form part of a wider scheme to create new rail links in west London and Surrey serving Heathrow, and would require the construction of an extra platform at Staines station.