The Government has given formal approval for the HS2 project to begin the construction phase.
It has issued a notice to proceed to the companies that will build phase one of the high-speed railway.
Prime Minister Boris Johnson gave the green light for HS2 in February despite it running tens of billions of pounds over budget and several years behind schedule.
The Government-commissioned Oakervee Review warned that the final bill could reach £106 billion at 2019 prices.
HS2 Minister Andrew Stephenson said: “While the Government’s top priority is rightly to combat the spread of coronavirus, protect the NHS and save lives, we cannot delay work on our long-term plan to level up the country.
“HS2 will be the spine of the country’s transport network, boosting capacity and connectivity while also re-balancing opportunity fairly across our towns and cities.
“Following the decision earlier this year to proceed with the project, this next step provides thousands of construction workers and businesses across the country with certainty at a time when they need it, and means that work can truly begin on delivering this transformational project.”
Notice to proceed has been given to the four joint ventures previously awarded main works civil contracts.
That means the firms can transition from carrying out scheme design and preparatory work to detailed design and construction.
HS2 Ltd chief executive Mark Thurston said: “In these difficult times, today’s announcement represents both an immediate boost to the construction industry – and the many millions of UK jobs that the industry supports – and an important investment in Britain’s future: levelling up the country, improving our transport network and changing the way we travel to help bring down carbon emissions and improve air quality for the next generation.”