Construction on controversial HS2 high speed rail line begins
Construction of HS2 will formally start on Friday with a "shovels in the ground'' moment.
Boris Johnson said the high-speed railway will create thousands of jobs and create vital links between urban areas.
Mr Johnson said: "HS2 is at the heart of our plans to build back better - and with construction now formally under way, it's set to create around 22,000 new jobs.
"As the spine of our country's transport network, the project will be vital in boosting connectivity between our towns and cities.''
The four main contractors for Phase One between London and the West Midlands will now switch from enabling works, scheme design and preparatory work to full construction.
The Government-commissioned Oakervee Review warned last year that the final bill for HS2 could reach ÂŁ106 billion at 2019 prices.
Despite it running tens of billions of pounds over budget and several years behind schedule, the PM gave the green light for the railway in February 2020.
The project was given a revised budget and schedule as part of his decision.
Two months' later, ministers gave the go ahead for it to enter the construction phase.
Transport Secretary Grant Shapps claimed Friday's event "marks a major milestone in this Government's ambitions to build back better from Covid-19''.
Construction will begin with the biggest engineering challenges - such as the stations and tunnels - followed by the main viaducts and bridges.
Most activity this year will be focused on HS2's city centre stations and major construction compounds such as in Old Oak Common, west London and Calvert, Buckinghamshire.
Phase 2b is set to connect the West Midlands to Leeds, which will run through towns and villages through North Derbyshire and South Yorkshire.
Campaigners have long called for the project to be scrapped, with homes under threat in some places- particularly on the Mexborough estate near Doncaster.