HS2 has been a controversial project since plans emerged in 2009.

Here is a timeline of key events:

– January 2009

Labour established HS2 Ltd to examine the case for a new high-speed rail line.

– December 2010

A consultation on a route for HS2 from London to Birmingham with a Y-shaped section to Manchester and Leeds is published by the Conservative-Liberal Democrat coalition government.

– January 2012

Transport secretary Justine Greening announces the Government has decided to go ahead with the project, despite concerns over its cost and the environmental impact of construction.

– November 2013

The Bill setting out the powers needed to build Phase 1 of HS2 between London and Birmingham is introduced to Parliament.

– January 2014

The Supreme Court rejects outstanding appeals by opponents of the rail scheme.

– November 2015

HS2 is given a budget of £55.7 billion.

– June 2016

The National Audit Office warns HS2 is under financial strain and could be delayed by a year.

– September 2016

Simon Kirby resigns as HS2 Ltd chief executive.

– February 2017

The Bill for Phase 1 achieves royal assent, enabling preparation work to begin.

– July 2017

HS2 Ltd accepts it was a “serious error” to make £1.76 million of unauthorised redundancy payments to staff.

– December 2018

Sir Terry Morgan resigns as chairman of HS2 Ltd amid criticism over his role as chairman of Crossrail, which is delayed and over budget.

– August 2019

The Conservatives commission a review into whether and how HS2 should continue, led by former HS2 Ltd chairman Douglas Oakervee.

– September 2019

A report by HS2 Ltd chairman Allan Cook says the railway may not be completed until 2040 and could cost £88 billion.

– January 2020

The Oakervee Review is widely leaked.

It finds that HS2 could cost up to £106 billion, but concludes “on balance” that the project should continue.

– February 2020

Prime minister Boris Johnson gives HS2 the go-ahead despite “exploded” costs.

The so-called funding envelope is reset.

Phase 1 is set at £44.6 billion (at 2019 prices), with the estimated cost for the full network revised to a range of between £72 billion-£98 billion.

– April 2020

HS2 Ltd gives formal approval for companies to begin construction of Phase 1.

– July 2020

The delivery of HS2 is given the highest risk warning by the Infrastructure and Projects Authority (IPA) for the first time.

– September 2020

Boris Johnson marks the project’s formal beginning of construction at an event in Solihull, West Midlands.

– January 2021

Environmental activists dig a network of tunnels in London’s Euston Square Gardens, resulting in a complex operation to remove them.

– February 2021

Legislation for Phase 2a of the railway – extending the line from Birmingham to Crewe – achieves royal assent, opening the way for construction to begin.

– March 2021

Anti-HS2 protests and the coronavirus pandemic have contributed to the project facing new “cost pressures” of £800 million, the Government announces.

– May 2021

HS2 launches its first giant tunnelling machine from a site in Buckinghamshire near the M25 motorway.

– June 2021

Concerns over HS2 are a major issue in a shock by-election defeat for the Tories as the Liberal Democrats win in Chesham and Amersham, Buckinghamshire.

– October 2021

HS2’s “cost pressures” have risen to “around £1.3 billion”, the Government says.

This is partly attributed to delays completing preparatory work, approving designs and securing planning consents.

– November 2021

HS2’s eastern leg between Leeds and the East Midlands is scrapped by the Government.

– January 2022

The Bill for Phase 2b, extending HS2 to Manchester, is laid in Parliament.

Transport secretary Grant Shapps hails this as a “landmark moment”.

– May 2022

Construction of the Colne Valley Viaduct begins.

It will be the UK’s longest railway bridge, stretching for 2.1 miles above a series of lakes and waterways just outside north-west London.

– October 2022

Levelling Up Secretary Michael Gove suggests capital investment for HS2 would be reviewed, but Chancellor Jeremy Hunt subsequently backs the project.

– March 2023

The Government announces that construction of the Birmingham to Crewe leg of HS2 will be delayed by two years.

Work at Euston is paused as costs have ballooned to £4.8 billion compared with an initial budget of £2.6 billion.

This means HS2 services will start and stop at Old Oak Common, west London, until at least the 2040s.

– September 2023

Prime Minister Rishi Sunak considers whether to scrap or delay the leg of HS2 from Birmingham to Manchester in response to soaring costs.