Morning brings us a few hours of free time in the city so we decide to check out the National Museum of Cambodia which is close to the Royal Palace. It’s a gorgeous building, full of fascinating artefacts from Khmer culture, along with devotional Buddha statues before which monks and worshippers pray and take selfies. 

At the heart of the museum is a tranquil courtyard, with a central Pagoda surrounded by lily ponds, and dappled with sunshine. We sit for a while in quiet contemplation, listening to birds singing and soaking up the morning rays, before wandering back to the hotel. 

We take a different route this time and stumble by chance upon a monastery called Wat Botum. It has an interesting arch and some intriguing stupas so we walk into the grounds, quite unprepared for what we find. Monks peek out of their rooms, smiling shyly at us, many with their orange robes drying on washing lines outside the buildings. 

But it is the central temple complex that blows us away. One vast hall in particular is rich with paintings and houses spectacular gold Buddhas, seated and reclining, with sunlight streaming through the incense-scented air. It’s far more impressive than the pagodas we visited yesterday and despite not being on any tourist map, we feel welcome in the peaceful surrounds. 

It’s baking hot so we take final advantage of the hotel’s lovely pool to cool down before our driver arrives at midday to transfer us to the river port where we meet Tsang, a slightly strange young woman, who takes us down a steep ramp to the Victoria ‘speedboat’; a motor launch that will transfer us straight from Phnom Penh to the Victoria Hotel in Chau Doc, Vietnam. 

Today we are the only guests making the journey so Tsang informs us it is our private boat, meaning it sets off as soon as we are onboard, a good 30 minutes ahead of schedule. As we watch the views of Phnom Penh’s towering modern skyline recede into the distance on the river, we are initially on the brown waters of the Tonlé Sap tributary. However it soon joins the bluer waters of the main Mekong, providing a rare spectacle where two rivers run side by side in different colours for a distance before they merge into one. 

The Mekong is one of the great shipping lanes of the world and as we speed down the middle we pass huge ships, sitting low in the water, transporting containers of goods, and every now and again the green and brown river banks give way to industrial complexes with vast cranes. 

Tsang tries to teach us some rudimentary greetings in Vietnamese, hovering at our shoulders and looking at us expectantly, but we struggle to understand each other; her English confined to a few phrases offering us lunch, or asking for passports, and our Vietnamese utterly non-existent. It’s a five hour trip, travelling 130kms, so once she finally gives up her silent presence staring at us from inches away, we settle in and watch the world go by. 

At Neak Loeng we pass under the longest bridge in Cambodia and eventually, three hours after leaving the capital we arrive at Cambodia’s rustic border and complete our exit papers, loading up on Saigon beer and some purple sweet potato crisps that have the tag line “Sooo glamorous” on the packet, but are so über-processed that they make Pringles seem like organic carrot sticks by comparison. 

A few minutes later, at exactly 3.47pm we wave goodbye to Cambodia and say “Good Afternoon Vietnam!” as we sail across the border point marked by national flags on the shoreline and pull into Vietnam’s floating immigration jetty. Passports stamped and visas checked we continue on our way in double-quick time - our private water taxi making this one of the smoothest border crossings we’ve ever done. Soooo glamorous indeed!

At the town of Tan Chou we turn off the Upper Mekong and head onto the smaller and quieter Lower Mekong, known as the Bassac River, to continue our journey to Châu Đốc, our destination for the next two nights in the heart of the Mekong Delta. 

It’s like turning off a motorway and onto a country road, the tankers and cargo boats replaced by fish farms, rice factories & mills on the river banks, with little wooden homes floating on water or on stilts on the shore. We watch people in the water using sandbags to prop up the collapsing river banks and solitary fishermen on boats hauling in nets, some wearing the famous conical Vietnamese hats. At one stage we even see a flock of pink ducks on the muddy banks, their feathers dyed to identify them as the property of a local farmer. 

Just after 5pm we dock at the Victoria Châu Đốc hotel, which sits at a bend on the river, with a another tributary feeding into the main flow and noisy motorboats chugging up and down. It’s very hot and humid and the sun is starting to set so once we’ve checked in and drunk the “whisky tea” (ginger, lime and green tea) they offer we spray ourselves with mosquito repellent and go for a walk.  

It’s a bit of a culture shock after the peace of our private boat. Châu Đốc is busy, noisy, dirty and poor, with a very different feel to Phnom Penh, not least with a completely different alphabet and street signs. Markets and street vendors are everywhere, litter piles up on pavements and shops are packed high with all manner of goods. 

Very much a local town, tourists are fairly thin on the ground, so we stand out as we stroll along taking photos of crowded backstreets and the market as it starts to close and dusk falls in the town. We find an ATM and become instant millionaires withdrawing 3,000,000 dong (about £100) before walking back along the riverfront promenade, with its giant statue of catfish - on which the local economy is built - and dodge little kids careering around in remote control cars to the amusement of their parents. 

It’s almost dark by the time we get back to the Victoria Hotel and we’re starving so we book dinner in its Bassac Restaurant, the smartest spot in town - not that there seem to be many options other than street food which, in this town, looks distinctly troublesome to Western stomachs. 

After a discussion with the staff, explaining that we are vegetarian, which definitely means no pork, chicken or fish - despite them all being listed as vegetarian options - we keep our finger crossed that the dishes we order are in fact suitable. 

We need have no fear - the pomelo, papaya and coconut salads are all delicious as is the banana leaf noodle dish with sesame crackers. In fact, it’s an excellent feast of fresh, light flavours that zing with citrus and chilli and rounds off the day nicely. I think we’re going to love Vietnam.