The Reunification Express links north Vietnam to the south. After spending 19 hours on it just to get half way to Danang, sometimes you’re glad to get off just to be reunited with various items of your personal anatomy.

Your luggage is of secondary importance.

Travelling 50km an hour at best but preferring the crawl default, the train is not express at all. Although it has a habit of suddenly picking up speed, throwing you up into the air and face-down in a stranger’s lap. Which is fine.

If you haven’t overdone the fermented fish sauce.

I spent the majority of the first part of the iconic train trip in the lavatory watching the tracks speed by below. This is not a very advantageous position for making penetrating observations about the Socialist Republic of Vietnam or composing lyrical descriptions of the Vietnamese countryside.

It had started so well too.

In Hanoi, after a lengthy and very straight-faced queue reinforced by armed officials making sure you don’t commit treason by smiling or wearing a hat, I paid  my respects to  the mummified remains of ‘Uncle Jo’ at the Ho Chi Minh Mausoleum and then visited  the Imperial citadel of Thang Long, Dong Xuan market, the water puppetry theatre, 1911 opera house  and the ‘36 Streets’ of the Old Quarter.

Between the Lake of the Restored Sword and Long Bien Bridge.

The ‘tube houses’ (3m wide by 60m deep) arose when shopkeepers were taxed according to the width of their storefront. Each street vaunts a speciality. ‘Hang (‘shop’) Gai’ silk clothing, ‘Hang Bac’ silver and jewellery, ‘Hang Ma’ paper products and ‘Hang Be’ bamboo handicraft. ‘Hang Thing’ is the wood turner’s street.

In hindsight, I should have spent more time in Loang Ong, the medicine street.

Or Hang Be.

But, at the time, I didn’t know I had picked up a parasite. If I had, I would have picked up a stomach settler or a conical ‘no la’ hat to throw up into.

The bug could have been airborne. The ammoniac Hang Mam Street makes ‘nuoc mam’. It’s also known for its coffin and tombstone makers. I began to feel nauseous walking beneath the pretty Xoan china berry trees through the fish sauce barrels along Hang Thung Street.

Once, napalm drifted menacingly across the country, felling anything  in their  way. Now it is the equally noxious and eye-watering ‘nuoac mam’. The foul-smelling sauce is made everywhere and served with everything.

They say that you will love Vietnam if you can stand the smell of nuoac mam in the morning. You must be prepared to be fascinated and nauseated. In turns.

But I was much better by Danang.

Danang is where the first Americans arrived in December, 1964. French sunbathers are now dug in along the beach. And para-glider squadrons patrol above it.

So pounded was it by artillery during ‘The American War’ that it became known as ‘Rocket City’. Originally called Cua Han (Han market), Danang was called Tourane after its tureen-shaped bay. Today it is ‘seaside-y’ with tacky beach restaurants offering local ‘fruits de la mer’ and nutritious novelties like ‘Teak and Chips’, ‘Fried Mongel Meat’ and ‘Sea Sludge Soup’.

The quirkiest souvenir available seemed to be cinnamon-scented foot cure-alls. (‘If Your Special Feet are still sweating, money back’).

Local hotels run jeep tours up into Cat’s Tooth mountains. The views are more impressive than the rubble. The religious centre built in the reign of King Bhadravarman in the fourth century was also a guerilla base and therefore bombed flat. An example of how the Americans, as one non-partisan writer put it, used “a sledgehammer to try to sink a floating cork”.

Not far away from Danang, past hundreds of giant prawn and shrimp nets, is the ancient town of Hoi An on the Thai Bon River. It’s big on what the guidebooks call ‘historical cultural vestiges’ (ornate pagodas and Japanese-made earthquake-resistant bridges), as well as tiny, elaborately grubby children selling postcards.

In a small bar I was served by a girl probably around 13. After she brought me a beer she went back to her book. It was an algebra book.

“Studying maths?” I asked, deliberately not saying math. She smiled.

“No. It’s the only book I have. Tourist gave me.”

The war years brought terrible hardship. During the post-war famine 3,000 tons of rice had to be brought in to feed the people. Post-unification things are improving through tourism.

You must be prepared to be fascinated and nauseated

Thankfully, I was eating again. The local speciality is ‘cao lau’, noodles with vegetables and slices of pork. This is traditionally washed down with snake wine.

Beside me someone was tucking into a bowl of boiled up golf ball and a fish head that looked remarkably like Andrew Marr.

There are some extraordinary looking fish in Vietnam. And some unforgettable sights in the markets. You can be browsing and come across Lee Hurst or Jon-Jo Shelvey curled up in a jar.

Mainstream non-celebrity look-a-like food includes cobra (‘ran ho’), bat (‘doi qua’), pig ear cartilage, sea swallow soup and duck’s blood custard.

Mist permitting, the high coast road from Danang through the Pass of Clouds to Hue is one of the most beautiful in Vietnam.

Across the spectacular Hai Van Pass you enter what one guidebook calls “the typhoon province of Quang Binh”. In 1945 the last of the Nguyen abdicated with the arrival of the Japanese. The Thien Mu Pagoda contains the taxi which took the ‘bonze’ or monk Quang Duc to Saigon where, in a famous notorious expression of dissent against the Diem regime, he set fire to himself in 1963. It was the first Buddhist protest suicide.

In the Imperial City of Hue you can eat aboard a dragon boat on the not so fragrant Perfumed River, Song Huong. You are escorted to your table and up the gangplank by a procession of drummers and waiters who bang on their drums to welcome you  to their world and the world of migraines and, more importantly, to concuss the local mosquitoes.

Hue was destroyed in the Tet Offensive of 1968. It was one of the bloodiest battles of the Vietnam War. A little over 2,000 American troops defeated 10,000 entrenched enemy troops, liberating the country’s cultural capital for South Vietnam.

The ‘Forbidden Purple City’ with the royal citadel and ‘Esplanade of the Great Welcome’ where mandarins would prostrate themselves (kow tow) in front of the emperor is, despite Unesco aid, is now no more than four large walls pock-marked by bullets and surrounded in summer by peach blossom and flame trees.

Upstream is the 17th century Elderly Goddess Pagoda’ and royal tombs. Locals will give you a lift on their Hondas if you are suffer from sampan-phobia.

Across the 17th parallel you have the infamous DMZ (Demilitarized Zone). After the Geneva Peace Conference of 1954 this was the five-kilometre No Man’s Land between north and south. Here the Americans established the firebases of Con Tieu, Doc Mieu, Khe Sanh and Ap Bia or ‘Hamburger Hill’, which made up the notorious  McNamara Defence Line set up to close the Truong Son Corridor or ‘Ho Chi Minh Trail’, the Viet Minh lifeline to the south.

A permit is necessary to see this area although local hotels can arrange guides around the killing fields of Mutter’s Ridge and Hill 400. Only a miniscule portion of the 16,000km Ho Chi Minh Trail can be visited. Unlike the Cu Chi tunnels, the Vinh Moc tunnels off highway Number One have not be widened to accommodate Teletubby-butted visitors.

The whole Reunification Express journey is around 1,700 kilometres and takes about 35 hours. For £40 you can get ‘soft sleeper’ bunks cabins with grey but clean sheets or cheaper ‘hard sleepers’ on rock-hard, wooden-slatted seats.

As the locals offer you nibbles of their chicken bones and the refreshment trolley serves ‘frog porridge’ the countryside slides by – rusty roofs, banana palms, yoked water buffaloes, paddyfield after paddyfield, motorbikes with three on-board waving and shouting their  smiling ‘Chao do’  hellos, which are far more memorable than  emperors’ tombs and temple complexes.

You start counting the bridge and give up at 37 out of 1,334. You count the tunnels, giving in after 16 out of 27. You get thrown in to another lap.

The track was laid for French colonists between 1880 and 1936. And rebuilt and reopened in 1976. It is one of the great train journeys of the world and I wouldn’t have missed it for the world. I may have been briefly incapacitated and missed the 17th parallel and Nam Dinh, the 10th-century capital.

But when I think of Vietnam I shall always think of Hue.