Just outside Paddington is a vast building site – turning a run down industrial area and old railway depot into a major HS2 railway station.

It’s a project that’s on a similar scale to the London Olympics in size, using a single impetus to regenerate an entire area, the arrival of a major railway hub. And yet, it’s just one, if surprisingly critical component of the mighty HS2 railway line.

HS2 is the controversial railway running through the country, but its largely controversial because most people don’t really understand why it’s needed. And that’s candidly a failing of HS2 themselves, and their political masters.

A railway costing as much as HS2 could just to shave 35 minutes off a trip to Birmingham is never going be popular. Even if with journey times of just 49 minutes, it could actually end up faster to get from Birmingham to Heathrow than from some parts of London to Heathrow.

But is it worth it?

It’s certainly a factor as Heathrow is a major hub airport for the UK and some flights only leave from Heathrow, so people who have to travel down to London will undeniably benefit from the new railway. More usefully for Londoners, it’ll become viable to fly from Birmingham, where flights can be cheaper, and without the air congestion, it’ll be more reliable than Heathrow.

In that sense, HS2 is not one-way traffic, sucking people into London, but making it much more viable to push jobs and services out of London. As was previously written, there’s some evidence that a reliable rail link between London and the regions means companies can shift some work out of expensive London into the cheaper regions — if the rail links are reliable.

Not necessarily fast, which is nice, but more importantly, reliable. The reliable bit is usually more important for people. Can I reliably arrive at the meeting on time, at the football match on time, at the wedding on time.

And that’s the core reason for HS2.

It’s a badly named railway — and they nearly changed the name a couple of years ago to get rid of the problem — as the High-Speed bit is a very small part of what’s being built.

As most people what the billions are being spent on, and they’ll say something like “it’s to knock 20 minutes off a train journey”, and unsurprisingly, that’s doesn’t sound like its worth the money and disruption.

Yes, if you’re building a new intercity railway, it makes sense for it to be very fast, but that’s just a thin layer of icing on a much larger cake and not really the main thing that HS2 is going to deliver.

It’s capacity. Oodles of new capacity.

The biggest problem affecting the railways today is a lack of capacity to handle the surging numbers of people who want to travel by train. So something needs to be done.

Yes, they could upgrade the existing lines, but that was tried with the West Coast Mainline Upgrade, and it delivered a fairly modest upgrade at a massive £14.5 billion cost. It’s possible, but not ideal to upgrade the old lines, but it provides many more benefits to build an entirely new railway line.

And, as they learnt with other attempts to upgrade existing lines, it can cost more per passenger mile of benefit to upgrade than to build from scratch.

Building from scratch means we can take advantage of modern engineering to build new rather than bolt onto old, and often bolting onto old means demolishing vast numbers of houses and factories that are right up against the existing railway tracks. Building new means a better railway for faster more reliable services without the clutter of the old suburban services.

And what that new railway will do is suck away the intercity traffic from the older lines, releasing huge amounts of space for more frequent services to be added connecting the towns. That’s the real reason for HS2 — it’s to improve the regional connections.

How that happens is that if you’re running intercity trains on tracks also occupied by stopping services, you need long gaps between the slow trains so that the intercity trains aren’t held up by the slower trains.

At the moment, sharing the tracks means that local commuter services are reduced to ensure the intercity trains can get through – which is great for the big cities, but hardly ideal for the regional towns and cities who struggle to fit in a regular train service.

So HS2 is about providing more space for more trains outside the main cities.

So while understandably the attention is on the big city connections and the high-speed service — it’s more about the overcrowded daily commuter services getting less crowded because more trains can run, and being more reliable because a small delay on one train doesn’t snarl up the entire timetable.

And here in London, that’s why both Euston and Old Oak Common are about to be rebuilt.

At Euston, it’s about fixing the bottleneck on the approach to the station. The station has enough platforms, but not enough railway tracks to get in and out, so trains have to wait for space in the tunnels to get into the station. And back out again. That’s a huge impediment to increasing the numbers of trains that commuters from North London and beyond can use.

Building not just more platforms for HS2, but critically, the extra tunnels for those trains to use shifts intercity services to the HS2 line, releasing lots of capacity in the old tunnels for suburban services.If that doesn’t sound too important, then where’s the UK’s most congested train… it’s the 17:46 out of Euston which carries more than twice the number of passengers that it’s designed for. When completed, HS2 is expected to more than double the number of seats out of Euston station during peak hours.

HS2 may sound like it’s all about fast trains to Birmingham, but for Euston passengers, it’s really about providing more trains from Watford and Milton Keynes.

That requires more suburban trains to be built, but the UK if anything has a bit of a surplus of capacity in that area. The big problem is a lack of railway to put them on — and that’s what HS2 is aiming to solve.

More space for more trains for more commuters.

So while Euston is the focus, as the London terminus of the line, you might wonder what’s the point of Old Oak Common station just a few short minutes up the road. Is it just there to trigger redevelopments in the area?

No — it’s absolutely critical to the reason for HS2 — to improve connections between regions and increase capacity.

Without Old Oak Common (OOC), the HS2 trains heading into Euston will be full of passengers who then need to be soaked up by the Underground. Yet, it’s estimated that as much as a quarter of the passengers using HS2 towards London won’t want to go to Euston.

They might be heading to Canary Wharf, or to Heathrow, or to Cornwall. The interchange at OOC means that people who don’t need to go into central London, wont have to.

The OOC station will provide connections through central London on the Elizabeth line, to north and south London on the Overground, to Heathrow and Bristol, and Wales on the GWR mainline.

So rather than heading into Euston, then looping around on the Underground to Paddington then back out again, the OOC interchange avoids all that — for the benefit of the HS2 passengers, and reduces unnecessary congestion on the Underground to Paddington.

While we’re told that HS2 all about North-South services, it’s also expected to reduce overcrowding on trains out of Paddington heading to Wales. And that demonstrates how HS2 is not just one fast line between some cities, but something that will improve rail journeys across the entire UK.

So, not far from Paddington has it happens, the Old Oak Common site is currently being cleared to receive its new stations.

A joint venture between Costain and Skanska is currently clearing area ahead of main construction starting. It’s a mix of old light industrial sites and the former Great Western railway depot.

It’s a grim-looking area, and even more so on a day when the heavens opened and dropped several months worth of rain in one afternoon. Meeting up with Alistair from HS2 and Tim from the Costain Skanska JV for a site tour, and an email ahead of a visit to bring an umbrella was not needed as the site is now so large – and on this day – so wet, that access is in a vehicle.

Three sites in total are needed to support the construction work — and when completed the two auxiliary support sites will be handed over for housing developments.

The old railway site has been largely cleared now. As you might expect for an old industrial site, they had to deal with asbestos in the goods sheds, but more serious were the decades of oil and lubricants that had soaked into the ground, especially in the service pits under the goods shed. A lot of that had to be dealt with by specialists and then disposed of carefully.

The rest of the site looks like huge piles of rubble, which is essentially what it is, but it’s piled up in graded piles to be used again. All the rubble has been having its metal rebar removed and been “cleaned” by local machines to remove contaminants and rather than shipping it off to a landfill, then shipping back clean aggregate later, they’ve got just about enough space here to store it for reuse.

And “just about” is the operative phrase, as the main HS2 site is surrounded by live railways – the Great Western service to the south and the Elizabeth line depot to the north and they need to squeeze the new station into this space.

A lot of the thinking going into the site at the moment is about how to ensure what they build today won’t block upgrades in the future. For example, although not part of the current plans, there will also be passive provision to add additional platforms for Chiltern Railway services to stop here in the future.

One thing you might not realise is that most of the images released recently of the new HS2 station at OOC are in fact, not the new HS2 station. They are the surface buildings for the Elizabeth line and GWR services, the HS2 platforms are underground.

They’re in the world’s second-longest railway box — the largest being in China, and only slightly larger, but as tempting as it might be to extend the OOC box a bit to nab the prize, that would be a vanity exercise. So HS2 is content with the title of second longest railway box in the world.

That box will serve several functions, as a station when finished, but in the early days as the launch site for the tunnel boring machines that will head towards Euston.

The spoil from those tunnels taken though a new side tunnel to one of the auxiliary sites, Atlas (after a local road) to be removed by the railway that just happens to be right next door. Although specifics are still being worked out, it’s likely that a lot of that soil will be used for landscaping along the HS2 route, to create artificial cuttings to reduce noise and provide bulking for land that will be regenerated as new woodlands and the like.

The Atlas site is huge, but also has a working cement supplier right in the middle who couldn’t be moved, so space is less than it looks.

This is where they will either store tunnel lining segments brought in from elsewhere or make them on site. It’s also the location where they took down two of the three huge yellow gantry cranes which had been a bit of a local landmark for many decades since they were last used.

The other location, known as the Victoria Road site, next to a former Waitrose warehouse, and here a huge shaft will be dug down and a gigantic crossover box created where the HS2 lines can cross if needed in the future. This will also be the launch site for the tunnel boring machines heading northwards out of London.

As there will be blocks of flats here when it’s all finished, they’re also investigating ways of taking heat out of the tunnels for the homes above.

They’ve taken over the neighbouring Waitrose site as well, to inspect delivery vehicles, and ensure they comply with safety regulations to improve cyclist safety and modern emissions standards for London.

In the early days, a handful of deliveries were turned back as the lorries didn’t follow the requirements, and since then, it’s not really been a problem. As with Crossrail, they’ve used the huge buying power of HS2 to force road safety improvements in the lorry trade.

While all this is going on, local businesses still need to keep working — such as the Lebanese restaurants and warehouses, the local residents nearby, and possibly oddest of all in this benighted part of town, the HR Owen service centre, which services luxury supercars.

Leading to the peculiar site of spotless supercars driving down roads occupied by huge building site vehicles.

Anyone who visits Old Oak Common or the nearby area cannot have failed to see how a formerly low-rise area is soaring skywards as property developers realise that this part of London will soon be one of the best connected in the country.

When finished, there will be a huge railway hub enabling people to head in almost any direction they want.

However, it cannot be denied that HS2 has been controversial.

It’s been badly branded as a high-speed line — derided as shaving a few insignificant minutes off trips for rich businessmen. No one ever seems to complain about making it easier for families visiting each other, it’s always the rich business men. Anyway, HS2’s so much more than that — and the impact is magnified many times over by the way it’ll improve the daily commute for vastly more people than will ever use HS2.

The costs are running rampant at the moment, but a project of this size was always going to find unexpected issues that simply couldn’t have been found in the relatively swift preparatory work done to get the line approved by politicians.

We should look at this as a long term investment.

At the moment, borrowing costs for government debt is at record low levels, and any government that didn’t take advantage of that to invest in infrastructure today for the future would be very odd indeed. Building HS2 today is much cheaper than building it tomorrow when debt costs will be higher.

Whatever the cost ends up being though, think about how long HS2 will last – this is not a generational project, but a multi-century investment. The original railways build in the 1830s are still in use today. Obviously they’ve had investment in signals, power supplies, trains – but the underlying structures are still there, and still in use.

That’s what HS2 will deliver — a railway that will still be in use in 200 years time. It’s a long-term investment of the sort that we really should be proud to be building in the UK.

And as it’s going to last 200+ years, let’s do it properly.