Ministers have moved on to a new track to help sell the HS2 project

The HS2 project has recently come under criticism from the Public Accounts Committee Photo: Press Association.

As I write, I am travelling on what is now called a "classic line."

It's how those planning Britain's new high speed rail line refer to the rest of the rail network.

Apparently, the extra capacity on my "classic line" as a result of HS2 (and a whole host of other factors) will deliver a £15 billion annual boost to the British economy.

That is the claim the government will make today as the Prime Minister and Transport Secretary launch what they themselves refer to as a "fightback."

Fightback? Because the £42 billion project to build a high speed train line from London to Birmingham, Manchester and Leeds has come under sustained pressure over the summer.

Reports have criticised the cost-benefit analysis. Ex-ministers who gave the project the green light now say they no longer support it. MPs told the government that it was not presenting "a convincing case" for HS2.

This morning, David Cameron tweeted:

It's clear Whitehall had concluded this line was heading into the sidings and ministers have moved onto a new track in an attempt to sell the project.

Today, the Transport Secretary, Patrick McLoughlin, will even admit, "the reason we need HS2 isn't for it's speed."

He will add: "the point about High Speed Two is that you won't have to travel on it to gain from the better transport system and economic growth it will support."

He will also attempt to take on critics who say the money would be better spent elsewhere on the transport system by claiming the government is already spending £24 billion on the roads and £37.5 billion on the existing rail network between 2014 and 2019.

An artist's impression of HS2.

However, I can't help but wonder if the new report by accountants KPMG has adopted a whole new methodology to make the answer fit the question.

It also attempts to counter the argument that London will get all the benefit and the line will suck the life out of the regions and into the capital.

It claims that Birmingham's economy will grow between 2% and 4%, Manchester up to 1.7%, Leeds up to 1.6% and Sheffield up to 3.2%.

The London economy by contrast will grow by only 0.5%.

The figures are based on the completion of the entire Y-shaped route in 2037.

How does it arrive at this figure?

KPMG suggests the extra capacity in the "classic" lines, the easier access to labour and a wider availability of suppliers will help companies in the producer and consumer services to compete more efficiently.

However, the public, many MPs and lots many business will need a lot of convincing before HS2 is firmly back on track.

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