There are certain assumptions you make about train travel in Europe, and one is that the purchase of a ticket will be relatively straightforward.

Giraffes, spooked by the rattling carriages, cantered away to the safety of the acacia trees... It was a safari by train, utterly magical- Helen Raine

I was assured by several friendly and smiling Zambians that the same applied to Tanzania-Zambia Railways, so much so that there was really no need to trouble oneself booking in advance. All you had to do was turn up at the rather remote Kapiri Mposhi Station an hour or so before the train left and buy a ticket.

There was one fairly essential piece of information that they omitted to tell me, however. This was only the case for third class travel.

For a normal journey, this would have been no big deal. By this point in my trip I was used to cramming my posterior into a space the size of a postage stamp on the bed of an open-back truck, surrounded by rice sacks, chickens and an impossibly large number of fellow travellers all eyeing me with amazement.

I had also travelled for hours in an overcrowded minivan with blacked-out windows and seats that leaned backwards, for maximum disorientation and claustrophobia. For most of the journey, I was holding someone else’s baby; I could rough it.

But travelling across the vast expanse of space that separates land-locked Zambia from the coastal capital of Dar es Salaam in Tanzania is no ordinary journey. I was to depart on a Tuesday afternoon and would be aboard until Thursday lunchtime; it’s a mammoth trip and third class is not how you want to do it.

The chaos surrounding the ticket desk should have given a clue as to how the booking was going to go. The perspiring ticket clerk, when I finally reached him, was hunched over a box of curling, ragged Kwacha notes, with a pen jammed into the corner of his mouth.

He leaned forward briefly, the better to hear my request, then flung himself back on his creaking swivel chair and laughed genially. “Mammi!” he exclaimed. “There is no first class left.”

I hastily revised my expectations of flitting across the plains in palatial comfort. “OK”, I said. “Second class then.” He was already shaking his head slowly from side to side and chuckling ruefully before I’d finished. “Only third class.” I had to get to Dar es Salaam to meet a friend for a safari and this train was the only option. I handed over the Kwacha.

It was only when I was standing on the platform, watching the train pull in that the full implications of being in possession of a third class ticket hit me. While porters helped the first class passengers aboard, I was nearly knocked over by a stampede of passengers towards the doors. The train had not even stopped before people were streaming into the corridors.

I soon understood why. Third class is not just a little more cramped than first and second; it’s the difference between a grossly overcrowded rabbit hutch and a palace.

Seating consisted of a single bench running down the side of the train. By the time I got on, finding a seat was not the issue; getting into the carriages at all was utterly impossible. People were jammed into every available pocket of space, along with their possessions, farm produce and livestock. I had literally no choice but to disembark and try to get into a carriage in forbidden first class.

The ticket clerk was right that all the tickets had been sold, but that didn’t mean every seat was taken. Within a couple of minutes, I came across a man in an expensive suit sitting alone in a compartment. With a nerve born of desperation, I pulled the door open and asked him if I could join him.

He raised an eyebrow and waved me in. It transpired that he was a government minister, bound for Tanzania on official business, and he was polite enough not to shoo a scruffy upstart tourist out of his cabin (it’s hard to imagine that happening in any other country). His four wives were travelling in a different compartment.

After a couple of hours of travel, he took me to their cabin to cajole two of the women into sharing a bed. I took the vacated berth with guilty gratitude.

So after the obligatory bribing of the guard to upgrade my ticket, I settled in to watch two days and two nights of Zambia gradually slip by into Tanzania.

The train was an express, but it regularly stopped at stations, often, it seemed, for no better reason than to allow the local people to sell food through the windows. I bargained so often with women toting their goods in baskets on their heads for hard boiled eggs, I couldn’t eat them for weeks afterwards.

Newspaper wraps of rice and cabbage, local biscuits and sweets were also thrown through the windows, even while the train was gathering speed; the vendors would run alongside for payment until the platform ran out.

The wives also shared what they had; delicious home-cooked food served from enormous lidded vats hidden under the beds.

Unfortunately, all I had to offer in return were Marmite sandwiches. One lady, resplendent in a vibrant African print dresses and headscarf sniffed the proffered sandwich suspiciously then one took a bite.

Her jaw dropped in horror. She chewed twice, shaking her head vigorously and unleashed a torrent of upbraids on the foulness of the stuff which rose higher and higher, until in panic, I grabbed the remainder and ate it just to convince the women it wasn’t a joke. Mollified, they stared on, tutting in amazement at the folly of the European.

Zambia is a beautiful country, but it was when we passed the border into Tanzania that the scene from the window got wild. The train runs through the Selous Game Reserve and the journey turns from an interesting jaunt through Zambian villages and bush into one of the most astounding train trips on earth.

Giraffes, spooked by the rattling carriages, cantered away to the safety of the acacia trees. Elephants flapped their ears against the dust and heat and watched the train warily before returning to feeding.

Herds of zebra streaked by metres away from the tracks and innumerable monkeys, baboons and antelope wandered through the long grass. It was a safari by train, utterly magical.

Miraculously, by all accounts, our train arrived more or less on time, creaking and groaning into the station at Dar es Salaam. The wives took their leave with a very poor impression of European cuisine and were whisked away by the government minister.

I plunged into the morass of people offering to carry bags, sell more eggs (an offer I firmly declined) or provide accommodation.

And behind me, the third class carriages opened, spewing crumpled but cheerful passengers and their possessions onto the platform for long after I’d headed for the sanctuary of a hostel.