Work has begun on a 10-mile long tunnel in Buckinghamshire for the new HS2 rail line.
The project’s first giant tunnelling machine, at 170m long, launched on Thursday (13 May) to dig a tunnel under the Chiltern Hills to make way for the controversial new rail link.
It is planned that the railway will connect London with the Midlands and the north of England, with Phase 1 connecting the UK’s capital with Birmingham.
Government ministers have hailed the project as “transformative”, while its critics argue that the cost-benefit can’t be justified.
So, what is HS2, what route will the rail link take - and why is it so controversial?
Here is everything you need to know.
What is HS2?
HS2 is the high-speed railway project that launched in September 2020.
It is planned that the line will link London, the Midlands, the north of England and Scotland by serving over 25 stations - including eight of Britain’s 10 largest cities.
When complete, the UK’s biggest infrastructure project will connect around 30 million people.
Six new train stations, including Birmingham Curzon Street and extensions for London Euston and Manchester Piccadilly, will be constructed for the railway.
The idea was first discussed by the government more than a decade ago but was eventually given the go ahead by Boris Johnson.
However, it could be 2040 before passenger services are operating throughout the full network.
The aim is for 18 trains an hour to run to and from London at speeds of up to 224mph, which is faster than any train service in Europe.
The project follows the development of HS1 - the high-speed railway line between London and Kent that connects the UK to routes in Europe.
What is the HS2 route?
Its construction is split into three phases. Phase 1, which links London and the West Midlands, has begun.
For that phase alone, more than 300 bridges and 70 viaducts will need to be built.
Then, work will start on Phase 2a, which will link the West Midlands and the north of England via Crewe. Phase 2b, which is the eastern leg, will be constructed to Manchester and Leeds.
Stations on the first phase of the new line will include London Euston, Old Oak Common in west London, Birmingham interchange and the brand new Birmingham Curzon Street.
The second phase will see high-speed trains heading northwest to Manchester Airport and Manchester Piccadilly, or travelling on existing lines through Wigan, Crewe and Stafford.
Trains will also go northeast from Birmingham towards the East Midlands Hub at Toton. From there, they will head on the HS2 line to Leeds, and other trains will diverge onto existing lines via Chesterfield and York.
The aim is to start running partial services on the Phase 1 line between 2029 and 2033, while services on the full network and Phase 2 will open between 2036 and 2040.
Why is the high speed railway controversial?
Governments have claimed that HS2, which will be mostly paid for by the taxpayer, is a good investment for the UK.
Ministers insist it will deliver growth in England and have a positive impact on jobs by creating more than 22,000 roles throughout its construction.
It is also hoped that the high speed rail project will reduce passenger overcrowding and help to rebalance the country’s economy through investment in transport infrastructure outside London.
Boris Johnson said HS2 would "fire up economic growth and help to rebalance opportunity".
However, the cost of the project has spiralled since it was first mooted.
At the time of the 2010 election, estimates put the costs at upwards of £20bn.
However, the latest progress report revealed that the total cost of HS2 could be around £98billion.
Those who oppose the project say this sum of money could be spent on improving rail capacity elsewhere.
Environmentalists are also concerned over the loss of green land and ancient trees, and that the railway will damage sensitive wildlife sites.
The campaign group Stop HS2 has called for the project to be scrapped, claiming it is over budget and behind schedule.
A review into the project, led by former HS2 chairman Douglas Oakervee, was launched in August 2019 to determine whether the project should proceed.
The report advised cancelling HS2 and argued that the rail network would benefit the transport system in the UK. It also said there were no “shovel-ready” alternative upgrades that could be carried out on existing railway lines.