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The UK Government should have funded electrification of the Great Western Mainline all the way to Swansea, as former Prime Minister David Cameron once promised to do. It's as simple as that.

While Transport Secretary Chris Grayling is right that bi-mode trains will mean that journey times between South Wales and Paddington will be the same as if the line had been electrified to Swansea - as opposed to just Cardiff - the cost would have been a drop in the ocean compared to the ten of billions that will be spent extending the HS2 network in England.

The next phase will see trains capable of speeds up to 200mph reaching Birmingham from London, with the next phase taking them to major cities and towns in the north of England, including Manchester and Leeds.

While the spiralling cost of electrifying the 60-mile stretch between Cardiff to Swansea had reached £700m - and there would be a healthy overspend contingency in that - England's high speed project has a price tag of £400m a mile .

Here's the stark truth: the entire cost of upgrading Cardiff to Swansea would get you just over 1.5 miles of HS2 track.

And let's face it, rail electrification is hardly groundbreaking transport technology. It was talked about for the Valley Lines back in the 1930s.

And that's why all of Wales needs to be making a strong and united case with the south west of England for high speed to come westwards as a priority.

One of the investment selling points of Bristol and South Wales, against Manchester and other northern cities, is their closer proximity to London and one of the world's biggest financial centres.

Even with direct trains from South Wales to London, high speed reaching the north of England will negate this advantage.

So high speed getting to the north of England and not westwards will be bad news for the economies of South Wales and the south west of England.

A report by consultancy Greengauge concluded that delivery of high speed 2, even with reduced journey times from electrification of the Great Western Mainline - would up to 2040:

See Wales having 21,000 less jobs.

0.04% lower annual growth.

£600 average lower incomes.

So where is the rallying cry from Wales and south west of England to bring high speed rail westwards? Why can't that be at the forefront of the UK Government's transport investment priority thinking?

If you don't ask, you certainly don't get. And it doesn't sound like anyone's asking with much volume at all.

Simply pressing for a Barnett formula consequential for the Welsh Government's block grant as a result of HS2 investment in England is pretty lame.

poll loading Should the UK Government make high speed rail coming to Bristol and south Wales a priority? 0+ VOTES SO FAR Yes No Don't know

We need the elected mayor of Bristol , the new Metro Mayor for the west of England, local authorities on both sides of the Bristol Channel, the Welsh Governments, MPs , Secretary of State for Wales Alun Cairns, the Welsh Government, businesses, universities, the general public - and more besides - to come together to make the case.

If the UK Government is serious about trying to re-balance the UK economy - which doesn't mean curtailing growth in the south east of England but ensuring that the growth trajectory of economies of other UK regions and nations are the same path - then it needs to be far bolder on transport investment.

High speed train journey times of less than an hour from south Wales to London, would provide a huge boost for the region's economy.

And while it would need a massive amount of investment - and any preferred route would no doubt face legal challenges from objectors - there is no reason why a high speed line from south Wales and Bristol to London - via Heathrow Airport - couldn't be delivered in a similar time frame to high speed reaching the north of England.