Sweet mother Mekong ain't sweet no more.

In 2017, Sue Perkins took a trip down the Ganges river and made a television programme about it. I watched it, enjoyed it, and for some reason wrote a blog about it. Three years before that she'd taken a trip along the Mekong so when BBC4 decided to repeat the four part series she made about that, I decided to respond in the same fashion even reworking the original blog title, despite the fact it no longer even vaguely works as a pun. Ah well, I have my protocols. I can't expect you to understand them.

But it's not about me (well it is really, it always is), it's about Sue, it's about the Mekong river, and it's about four of the countries that river flows through: - China, Laos, Cambodia, and Vietnam. With the Ganges she went source to mouth. With the Mekong she's going way upstream in the opposite direction. Variety, as they say, is the spice of life. That and having a cushy job as a BBC travel correspondent. Not that I'm jealous.

Okay, I'm jealous. The first of four episodes sees Sue, who it must be said has quite an astonishing range of puffa jackets - the most noteworthy being a navy blue North Face affair and a silvery grey Arsene Wenger sleeping bag number, in Vietnam's Mekong delta where she'll begin her 3,000 mile to that river's source in Tibet.

Here "the mother of water" is neither remote nor pastoral but dirty and brown, which doesn't stop people from washing their clothes in it. Colourful boats draped with tyres float quietly past wooden shacks on stilts and Sue arrives in Can Tho, with a population of over 1,500,000 the biggest city on the delta.

In Can Tho we're introduced to the 'Queen of the Noodle', we visit a market that sells mangoes, pineapples, and dragon fruit, we learn stuff about the mythology of a product called 'white gold' that you may well know as rice, and we see Sue having a crack at being both a rice farmer and a noodle seller. It's, for the most part, pretty lightweight stuff but the show does touch on some bigger, heavier topics.

It can't avoid them. The slowly rising sea level has been flooding the delta, described as "an artery for trade and travel", with salt water and rice doesn't grow in salt water. Prawn fishing is taking hold instead.

That's bad for rice fishermen and for prawns but on arrival in Cambodia the stories we hear are far far worse. 25% of Cambodia's population (just shy of 2,000,000) were wiped out during my lifetime by Pol Pot and the Khmer Rouge. Sue calls Phnom Penh "a place of endless contradictions" but there's nothing contradictory about the Khmer Rouge's year zero policy or the S-21 detention centre (now the Toul Sleng Genocide Museum), an ex-school where an estimated 18,000+ people were tortured and killed. It was just one of at least 150 torture and execution centres established by the Khmer Rouge. Not contradictory. Just vile.

Displays of rusty axes and other grim instruments are testament to an era, not so long ago, when people could be tortured for simply being educated. Pol Pot, it seems, had had enough of experts. Others were forced, under torture, to admit they worked for the CIA and when, in January 1979, Vietnamese troops liberated Phnom Penh, the Khmer Rouge (in a final act of gruesome savagery) shot dead many female prisoners. And the babies too. Before that, we learn when Sue visits the Killing Fields, bullets were too expensive to waste on babies so Pol Pot's troops simply smashed their skulls in.

It's an unrelentingly bleak warning from history (though one many seem unwilling to learn) but the age of the average Cambodian now is just 34 years old, born after the genocide, and life, for them, thankfully, is very different. A visit to Tonle Sap, the largest freshwater lake in all of SE Asia, is quite an eye opener. It's the size of Gloucestershire and when the waters flood it expands to four times its normal size.

Elsewhere in Cambodia, Perkins visits a puppet show in Siem Reap that lasts for three and a half hours (and I thought my kathakali experience in India dragged on a bit), she enters some daft boat race thing, visits a monastery barge (floating in a river full of piss and shit), and witnesses a snake killing expedition. Overfarming of snakes is depleting their population along with that of the resident crocodiles and fish.

For the most part our host is likeable, she's game, and she's curious. Her attempts to be funny are more affable than hilarious. Like a game show host or, yes, a travel correspondent. So she's well suited to the gig and the friendliness of those she meets makes it look like quite a fun piece of work too. I couldn't help wondering what a travel show in which a Vietnamese or Cambodian TV personality travelled around the UK would look like. Would we be so friendly? Judging by the way we're treating our European neighbours (and even ourselves - cf.Windursh generation) at the moment it seems unlikely.

To give you an idea of how long ago this show was actually filmed, when Sue Perkins arrives in Laos she meets a young lad in a Man Utd shirt (everywhere in the bloody world!) and asks him how he rates David Moyes's management of the Red Devils!

The saying goes that the Vietnamese plant the rice, the Cambodians watch the rise, and the Laotians listen to the rice. The riverine archipelago of Si Phan Don (meaning 4,000 islands) is beautiful even by the standards of the Mekong. This beauty has seen tourism, backpackers especially, taking over from fishing as the main source of income for the region.

You can enjoy a papaya salad, watch Buddhist ceremonies, or dance to Laotian music. Sue Perkins, of course does all of this. But when the Xayaburi Dam, the first across the lower Mekong, is completed all this may be under threat. It will totally block the river and it's just the first of many. Ten more are planned, and one hundred and forty others await confirmation, in Laos alone.

Perkins, like me, has mixed feelings about modernisation, progress, and capitalism and she speaks eloquently and articulately about those feelings. While I'm no fan of capitalism I do believe that the people who live in these areas should have access to basic sanitation, clean and safe housing, and maybe WiFi!

It's selfish to expect people to live in penury just so it looks picturesque, or Instagrammable, when us foreigners deign to visit. I visited Cartagena in Colombia with a friend once and he was horrified by the sight of a tower block near an old colonial district. He genuinely thought people should go without homes so his holiday experience could be enriched by their poverty (although to be fair to him, he didn't word it exactly like that).

I digress (as any traveller should be at liberty to do). As our guide spanks some river weed we learn that Laos is the poorest of all Mekong nations and has a 25% illiteracy rate. A floating library that takes books to remote river villages, some home to a few of the 49 different ethic minorities of Laos, seeks to change all that.

It's a heartwarming project and it's a heartwarming piece of television. The children of the Hmong people wait on the Mekong's banks for the library boat to dock and greet its arrival with a song before each grabbing a book, I spotted The Hungry Caterpillar, and taking it to a nearby rock for a very intense, and very touching, read.

Continuing northwards, Luang Prabang is an ancient city famous for its temples, its monks, and, now, its tourists. We're shown views of the UNESCO World Heritage Site from nearby Pussy Mountain, and we see people handing out sticky rice to the monks at dawn. Traditionally, every Laotian man is expected to spend at least a brief period of time as a monk.

On a two day journey north towards China the adjectives for the river just pour out. It's pure, it's timeless, it's untouched, and it's beautiful. That is, at least, until you reach the Golden Triangle. Long notorious for opium production but now pushing a drug of a very different kind. Gambling.

The casino we see, in a 'special economic zone', is a 'mausoleum of bad taste'. There's a statue of Zeus (gold, natch) and what I assume to be fake Michelangelo paintings. Laotians are banned by law from gambling in Laos and the Chinese are banned from gambling in China so this area, full of Chinese gamblers who can gamble in Laos, is in effect a Chinese exclave.

I wonder how long the ban on gambling will remain in place in China, as its 1,300,000,000 citizens move further and further into capitalism. Taking a jump that took Europe two or three centuries in two or three decades, virtually leapfrogging the Industrial Revolution, and heading towards being the world's most powerful country. Trump's doing his best to help to diminishing America on the global stage.

In Yunnan's capital city, Jing Hong, there is, it's hard to believe, an 'ethnic' theme park. 92% of the Chinese population are Han but in Jing Hong they can visit, and observe, the Dai people and see them partake in a mocked up version of one of their traditional water festivals. It's better than one hundred or so years ago when ethnic people were displayed in cages in a human zoo for Han Chinese to visit but it's still ethically pretty dubious.

From the water people (the Dai) to the tea people. People have been harvesting tea leaves, famously, in China since before the time of Christ but it's only recently that some have started getting seriously rich on the back of it. There are as many middle class people in China now as there are ALL people in the US and they like to spend their money, flaunt their wealth.

Alongside the newly wealthy middle classes though, there are people who eat squirrels (I didn't see them on the menu on my visit to China in 2005 but I did see donkey, dog, and 'nutritious beef penis in pot' as well as a lady cutting snakes heads off in a market in Xi'an), and there are the ethnic minority Aini people who have no written language so record their history using the medium of embroidery!

Judging by the ones we're introduced to on this cruise, they like a drink and sing-sing too. Good on 'em.

In Baisha the Mekong undergoes a name change and becomes the La Shang Jang (turbulent) river. Here we're party to a senior citizen's line dance (a memorable experience from my aforementioned Chinese trip is witnessing chefs partaking in a three-legged race in Datong) and we meet a highly enthusiastic practitioner of Chinese medicines and I start to wonder if I should get some chrysanthemum in for when I'm next struck by a bout of gout.

Heading up into the Himalayan foothills, and getting emotional - altitude will do that to you, the crew are forbidden, by the notoriously sensitive control freaks of the Chinese government, from filming the Mekong dams but what we do see of modern China looks like a building site that's been dropped from the sky onto paradise.

Among the lorries and industrial machinery, however, there are vineyards, brought to the country by French missionaries along with (surprisingly popular in the area) Catholicism. Buddhist prayer flags to pacify the Gods flutter along the windy pre-Tibetan ridges but, here, we're forced into a ludicrously lengthy diversion. China annexed Tibet in 1951, forcing the Dalai Lama into exile, and no foreign film crews are allowed. Maybe they should look into an ethnic theme park!?

It takes THREE flights to circumnavigate this and arrive back near the source of the Mekong on the high plateaus of Tibet where yaks (twelve million of them) outnumber people two to one. It's said it's lucky to tread in yak dung making it something of a Tibetan equivalent to pigeon shit.

The Nagayama monastery (I hope I've spelt that right, Google wasn't helping) near the source of the Mekong is our final destination. Here nuns and monks in crimson robes make offerings to the Nagas, or water gods, who, as so often is the case, have human feelings of jealousy, anger etc; and carry out human actions. Almost as if they were completely made up by humans.

Of course it's bullshit, but it's no more bullshit than any other religion or even the bullshit that I believe and write about. It helps these people navigate their way through life (and indeed along rivers - be it backwards or forwards) and we all have to do that as best we can, ideally without killing 25% of our countrymen. Sue Perkins was an able guide on this Mekong adventure. Let's see her have a crack at the Thames next!