The reason why the railways first were government owned is that there
was no way finance could be raised for such a large system with such
a small population in the 19th century.

The system today is so large that I doubt finance could be raised to
purchase it. To save fuel it will become necessary to ban long distance
road transport. That situation will almost certainly occur by 2023.
The necessity to build the necessary road/rail/road transfer
infrastructure may also require government finance, if not direct ownership.
At present rail freight has been privatised apparently successfully.
They pay a toll to the railway to run their freight trains over government track.

All in all, privatision is a very complicated business.

On the subject of Railways, in the future unless alternative sources of fuel, diesel are found, it may become impossible to transport goods on large scale over long distances without the use of rail.

I believe that some time in the future rail will have another golden age.

The use of loaded trailers with train wheels would be more simpler than train wagons. Once at their nearest destination they convert back to on road trailers.

Is rail actually any more economical in diesel fuel than road? When you consider the trucks at each end, it may not be.

Now if we are talking about steam, using our great reserves of coal, that might work, & steam trains are more romantic. Then again, fix the unions, & coastal shipping may become viable, under steam too.

On the other hand, give me a small [few thousand tonner], sailing cargo coaster ship to run, & I'll even come out of retirement to do it. That would be fun.

Hasbeen,
"Is rail actually any more economical in diesel fuel than road? When you consider the trucks at each end, it may not be."
It is.

Whether the fuel saving would translate to modal shift is less certain. Even where it is paralleled by rail, road does have the advantage of being able to go immediately, and can carry specialist loads that rail can not. So while more efficient terminals, new and upgraded lines and higher fuel prices will certainly shift some freight onto rail, long distance road freight will not disappear however high fuel prices get.

579; the use of rail wheels on road trailers was tried sometime back.
They were known as road railers. I suspect the idea failed because the
forces needed if it was necessary to reverse up on a grade are too
great for road trailers.
A thought about 100 of them backing up requires a really big push.
Both the US and the UK tried it.

Wooley B:
road trucks use 8 times the fuel that diesel locomotives use
per ton/km.
In future rail power will be electric.

Hasbeen;
Sea transport is even more efficient than rail.
It is the long distance mileage that uses the fuel, and Volvo and
Mercedes are trialing electric trucks for shorter distances.
I think using power stations and electric locos would be more efficient
and a lot cheaper than building a big fleet of big steam locos.
It might well use less coal.
Automatic road/rail/road container transfer equioment is already in use.