Today's song comes courtesy of Frankie. By the Guillemots apparently. And very appropriate because we are now in that very country having caught the train from Santa Cruz to the border. 600 km, about the distance from London to Edinburgh, and taking about 18 hours. Not the fastest train in the world.

But before all of that we have to get on it. This is not simply a case of buying a ticket and then walking onto the platform. First we have to pay a 'terminal tax'. This seems standard practice at Bolivian bus stations and seemingly train stations too. Tax duly paid we queue up to get onto the platform. A fat policeman with several gold teeth carefully checks our tickets and our passports. However he gets confused because Kate has the ticket with my name on and even though we are both together and showing him both passports it takes him a while to figure out that the picture in my passport is me and not her. But eventually he gets there and we are let onto the platform. Only for further confusion to ensue when he gestures at our suitcases and says 'too big' and points towards the left luggage. Are we not allowed to take it on the train? Well no, just that we have to put them in the luggage van for which we are charged (all of £1). Perhaps Bolivian railways are a subsidiary of Ryanair?

Bolivian travel companies have a reputation for not bothering too much about timetables. An unjustified one in our experience. Our flights and bus journeys have all departed just about on time. And the train is no different. Spot on 13.20 we're off. And it soon becomes apparent why the journey is so slow. As the train gathers speed it begins to pitch and roll like a ship in a gale. Evidently the track is not too well maintained and a speed of over 30 mph is likely to cause the train to derail and so it's a case of making slow and rather unsteady progress.

We are travelling 'Super Pullman' class. Disabuse yourself of any notion of tables with ritzy lamps, white linen tablecloths and waiters attending to our every need. But we do get reclining seats with leg rests, air conditioning, TV and 'ambient music'. For the first hour this turns out to be bad Latin American pop music, that wouldn't disgrace the Eurovision Song Contest, on the TV. This is followed by a series of progressively more preposterous and badly acted action movies most of which are dubbed. Frustratingly for the only one with subtitles the sound is turned down.

And so we bump and sway our way across Bolivia. We are now a long way from the Andes and the altiplano. Indeed we might be described as on the outskirts of the Amazon basin and the land is as flat as a pancake. "So flat you can't even stub your toe" in the words of one of the songs on my music player.

But it is not without interest. There is plenty of bird life to be seen - egrets, rheas, vultures and birds of prey. Every so often we stop in a small town and there is a bustle of activity as people get on and off the train. This is one of the few trains still running in South America that serves local people rather than catering for tourists. Unfortunately, unlike in India, you can't sit in the open door as the train travels along. Although given the tendency of the train to occasionally lurch in a rather alarming manner, maybe that's for the best.

By 7 o'clock it's dark and we retire to the buffet car. This is where the action is. Most of the tables are occupied by groups of women chatting away, playing games but not doing much eating and drinking. Still the buffet car man doesn't seem to mind although I suspect that Gate Gourmet who provide the on-train catering (couldn't they find a local company?) wouldn't be too pleased.

The train progresses on through the night making more occasional stops at dimly lit stations. No matter what the time there are still people getting on and off but given that the train only runs three times a week they don't really have much choice. Meanwhile I manage some fitful sleep but am interrupted by some of the other passengers. A woman in front of me decides that 1 o'clock in the morning is the best time to ring her friends and behind me another woman, who I think may be deaf, starts to play games on her 'phone with the sound still on. But I'm too timid to complain so put up with having my sleep disturbed.

Dawn comes at about 5 but we still have some way to go. The timetable is suspiciously precise stating that we will arrive in Puerto Guejjero, the end of the line, at 6.02 precisely. As it transpires we get there at 7.32 meaning that the whole journey has taken just over 18 hours. By my reckoning in Britain we could have travelled between London and Edinburgh four times in the same time.

But never mind we are here and, anyway, the border to Brazil doesn't open until 8 so being late doesn't matter too much. Except that it means we are further back in the queue. We have been warned that getting across can take up to 6 hours, the man selling bus tickets looks at our position in the queue and says three. By eight o'clock the temperature is already rising fast - our taxi driver said it was predicted to reach 45 degrees today. Can I stand for 3 hours in such heat?

Well, it turns out that the question is academic. Because we are 'old' (over 60) we can jump to the front of the queue for both Bolivian and Brazilian immigration! I feel a pang of guilt as we walk past the long queue of waiting people that seems to be moving nowhere - but it doesn't last long. No one seems to complain about the preferential treatment we receive - indeed several young people enthusiastically indicate that we should take our rightful place at the front of the line. Ah - respect at last! But I can't see it happening in Britain.

And so by just after 9 we arrive at our hotel - the strangely named 'Hotel Gold Fish' and have a well earned sleep.