HS2, in turn, has now signed off the four major civils contracts, worth a total of £12bn.

A dozen firms involved can now start work immediately, progressing detailed design, site preparation works and placing key subcontracts.

Contractors have been reviewing their ability to work within Public Health England guidelines to ensure the health, safety and wellbeing of the workforce.

To date, the four main consortia have focused on undertaking scheme design and site preparation, including pricing and scoping.

Work can now transition from scheme design and preparatory work, to full detailed design and construction, creating thousands of new jobs.

Mark Thurston, CEO of HS2, 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

“HS2 has been over ten years in development and design.”

He added: “While the country’s focus is rightly on defeating COVID-19, the issuing of Notice to Proceed today ensures that our contractors and their supply chains have the confidence that they can commit to building HS2, generating thousands of skilled jobs across the country as we recover from the pandemic.”

The long-awaited decision was greeted with relief among major contractors.

Leo Quinn, Balfour Beatty Group chief executive, said: “Notice to proceed provides certainty for many businesses up and down the UK, and will drive investment in skills and capability for current and future generations.”

He added that preparatory works were due to start imminently with main construction to commence in earnest in the second quarter of 2021.

All sites will be fully compliant with UK Government guidance for safe working practices in relation to social distancing.

At construction peak, Balfour Beatty/Vinci will employ a workforce of over 8,000, many of whom will be locally employed.

In addition, Balfour Beatty VINCI will offer approximately 400 apprenticeship and graduate opportunities.

Stephen Fox, chief executive, BAM Nuttall said: “The Notice to Proceed for HS2 is extremely positive news, particularly at this difficult time for the country.”

Skanska estimated its consortium contract alone would create over 6,000 jobs. This is made up of 1,500 in the joint venture and over 4,800 in the supply chain.

Costain’s share price jumped over a third in early trading after the news.