Privatisation has thrown up many anomalies in how Britain travels by train. We’ve all scratched our heads at how single fares can cost the same as returns; trips to Scotland can turn out cheaper than an awayday to Birmingham.

But there’s another way the free market has bizarrely contorted the natural order: the state of the very trains we sit in.

If you are reading this on a South Western Railway service on the Windsor line out of Waterloo, the chances are you’re sitting (or standing) in a brand, spanking new carriage.

Built by Siemens in Krefeld, Germany, it is known as a Desiro City Class 707 and only entered service in the past few months.

The previous operator of your line, South West Trains, decided to order 30 of them back in 2014 to expand the Waterloo fleet.

Trains take a while to build, so deliveries only began towards the end of last year, with the last one expected to be finished and carrying passengers in the next couple of weeks.

Lucky you. But don’t get used to them. For, despite the fact that trains are built to last at least 30 years, these 150 carriages will be out of service by the end of next year.

Why? Because the franchise changed hands and the new operators (FirstGroup and MTR) have struck another deal to replace them all with an even more brand new set.

Thanks to the bizarre nature of the train world, it has become cheaper for them to get an entirely new batch of rolling stock than to continue with the present “new” ones.

Let me explain. When rail was privatised three decades ago, John Major’s government created a set-up where trains would be owned and maintained by one lot of companies but operated by another.

Train operating companies, or TOCs, would run them under franchises of around seven years, leasing them from the owners — rolling stock operating companies, or Roscos.

Still with me?

The separation was done because the government wanted to keep franchises relatively short, hoping to foster regularly refreshed competition and make it easier to calculate the value of the contract. Given that trains last 30 years, it made sense for them to be financed, owned and serviced by separate companies.

Famously, the trains were sold way too cheaply to the three Roscos, Porterbrook, Angel Trains and Eversholt Rail, which made themselves fortunes in the early days.

Now, though, the pendulum has swung against the establishment trio. First, low interest rates mean it is cheaper than ever to borrow the money for buying trains. This has attracted new competitors into the market to take on the old Roscos. They have raised billions of pounds from pension funds wanting to invest in that most zeitgeisty of asset classes, “infrastructure”.

Second, huge competition among train-makers means businesses such as Siemens, Bombardier and Stadler have been forced to cut their prices. One source says prices are at their lowest since the early 2000s.

The TOCs can barely keep a straight face: “We’ve never had it so good,” says one director. “And it’s about time the boot was on our foot.”

So, it has worked out cheaper for South Western Railway to ditch the brand new Waterloo-to-Windsor 707s South West Trains leased from Angel Trains for “new” new trains from one of the newcomers to the leasing world, Rock Infrastructure.

Over at Liverpool Street, it’s the same story. Greater Anglia is ditching the Bombardiers it leased from Macquarie to run the Stansted Express despite their being only six years old.

Similar cases abound, leaving leasing companies scrabbling to find new operators to take their nearly new trains.

Why don’t they just park them in a sidings somewhere and wait for the market to turn? Because, as Angel Trains chief operating officer Kevin Tribley says: “That costs money. Trains are like cars — they don’t like just being left. You have to keep servicing them and looking after them.”

Not much fun when you’re not getting any rental income.

Tribley says he’s working hard to find new operators for his 707s: “It would be a crying shame if, in a country where trains are full of passengers, brand new ones like ours weren’t being used.”

Tony Lodge of the Centre for Policy Studies think-tank has another name for it — “madness”.

He says the present Government should allow new, smaller companies to run these nearly-new trains on local routes in semi-rural locations currently underserved by the big franchises.

Take the East Coast Mainline, he says. Two new companies, Hull Trains and Grand Central, launched services to towns such as Hull, Sunderland and Bradford which had long been denied direct services to London.

“They were able to make it work financially because they leased slightly older rolling stock. But passengers don’t mind; the trains are perfectly decent, and mean they have an alternative to driving.”

Whether the Transport Secretary Chris Grayling heeds Lodge or not, all this market pressure on the Roscos is a rare bit of good news for passengers facing ever-higher fares.

This year will see the biggest number of brand new trains coming onto our rail network ever. As one train operator says: “This is one example where the free market in rail is really working for the public.”

That doesn’t mean, though, that there aren’t negative consequences for the country.

Porterbrook, Angel and Eversholt, with their fleets ranging from brand new to 20 years-plus, are the biggest users of Britain’s rail engineering industry. Tens of thousands of British jobs rely on Roscos re-engineering mid-life trains and keeping them in service.

With so many shiny new ones coming into the system, those jobs will dry up. For a Government which considers rail as a core plank in its industrial strategy, that’s bad news.

Furthermore, as far as servicing goes, the new generation of trains are like modern cars. Less get-out-your- spanner, more plug-in-your laptop. Britain’s engineers need reskilling for the time when today’s new trains start getting old.

Perhaps, you might say, that time will never come: trains will just keep being renewed every few years — Britain will become the Peter Pan of rolling stock.

Unlikely.

Whether it’s an established player such as Angel Trains or a newcomer like Rock, all leasing firms rely on investors to finance their trains. If lenders see many more situations where their brand new trains are being shunted off into the sidings gathering dust and no rent, they’ll soon begin to charge more for the added risk.

And that’s before the Bank of England starts putting up interest rates.

As one Rosco director puts it: “There’s no doubt, the market is currently in a bubble.”

We all know what happens to bubbles. Newbies like Rock might want to bear that in mind.