THERE is a myth being peddled about High Speed 2 (HS2) — that it’s only now “decision time.” Nonsense — the decision to go ahead was taken as long ago as 2012 and indeed this vital rail link is already being built today.

Let’s face it, the only reason we are still discussing its future is because Boris Johnson ordered a review to please his backbenchers. Led by Douglas Oakervee, it will be made public and decided upon next month — though its findings have already been leaked.

What we know is Oakervee himself is backing HS2 and he is the person who has drilled down into the evidence. You can hardly blame him given that nearly half of Britain’s population would be linked to HS2 services around Manchester, Leeds, Birmingham, London and beyond.

I want to say directly to the Prime Minister — there must be no going back, no caving in to Tory MPs who can’t see further than the bottom of their own garden. Let’s put an end to the dithering which has gone on for too long, and instead have a full-throated commitment to HS2 from this government — and let’s take it all the way to Scotland.

Those against must tell us what they propose as an alternative, for again Oakervee accepts that no other major project is shovel ready and able to deliver benefits to the Midlands and the north of England as quickly as HS2.

Ignore the recent rows about finance — all large-scale infrastructure projects incur significant costs. That is an inescapable fact of life which doesn’t stop high-speed rail being delivered in Germany, Spain, France, Japan and many other countries around the world.

Instead we should look at what it offers in the long term, to understand its true value. Coolly examined, the case for HS2 is overwhelming — it’s game changer for Britain.

For a start, high-speed rail from London to the north is long overdue, with both business and communities suffering in its absence. Public investment through HS2 will be a once in a generation boost to the heart of our country creating half a million new jobs and thousands of homes, mainly in the north and Midlands.

However, this is not just about economics — the introduction of HS2 would overhaul our transport system which is creaking after more than two decades of failed privatisation. This is about using a state of the art high-speed network to shift freight and passenger travel from road to rail, cutting our carbon emissions and fighting climate change.

For too long the north of England has been the poor relation when it comes to investment in transport. For this to change HS2 must be given the green light. Make no mistake, now is the time to be bold and proudly grasp this golden opportunity to bring our railways into the 21st century.

It’s also important to remember that investment in HS2, Northern Powerhouse Rail and Midlands Engine Rail is happening alongside nearly £50 billion earmarked for modernising the existing rail network.

Scrapping it and just upgrading existing routes simply doesn’t get us very far down the tracks or provide anywhere near the badly needed extra capacity HS2 will bring. It would mean huge and lasting upheaval across the west coast, midland and east coast mainlines resulting in weekend closures for 15 years. Even then, at the end of all that, some capacity may have been added but very little extra connectivity.

Again, the message is clear when we look beyond the Westminster bubble and hear from the political and civic leaders of those areas which have so much to gain from this project.

They all want HS2 because they know it’s the key to unleashing the full economic, social and cultural potential of these regions. As the Labour Mayor of Greater Manchester, Andy Burnham has rightly said: “If Britain talks itself out of building HS2, I think we will be making a major mistake.”

If this Prime Minister is so keen to “level up” the country, he must realise that HS2 will go a long way in doing just that.

Forging ahead with HS2 will help to shape the decades which lie ahead, when it comes not only to clean and green high-speed travel on a par with other developed countries, but also the creation of jobs and the flourishing of economies across the Midlands, northern England and Scotland.

In short Prime Minister — it’s time to get HS2 done.

Manuel Cortes is general secretary of the TSSA.