Just as we get close, the heavens open once more, and we find ourselves cowering under little awnings as we try and make our way down neon lit streets, past little stalls selling steaming hot bowls of pho and rice to backpackers sitting on plastic stools trying to escape the downpour. It’s like a scene from Blade Runner, a vision of dystopian future, where humans huddle together in rain-soaked, over-crowded Asian back alleys.

It’s raining and to make matters worse, our first leg takes us out of Haiphong up over an enormous suspension bridge that’s so steep that every rotation of the pedals is a struggle and the wind and water splashes and freezes us as we climb to the crest and then freewheel down the other side. At the bottom, we make a sharp-right turn, away from the traffic but down bumpy terrible tracks, breathing in the pollution and dodging rocks as we go.

This part of Vietnam rarely sees tourists, especially Westerners, and as we all fly past on bicycles, in our varying states of age, size and fitness, the locals gawp and laugh, sticking their thumbs up and cheering us on, crazy lunatics that we are. It helps that we’re all dressed in red t-shirts with gold lettering; the Tet colours of luck and prosperity, so we appear to be blessing the villages with New Year greetings as we barrel through at speed.

What follows that afternoon though is the vision of rural Vietnam I had in my mind, as we cycle off road through the beautiful Ninh Binh countryside, taking in the majestic limestone rocks and gorges, the snaking rivers along which women row boats of intrepid tourists with their feet. We push on in single file, our bikes taking a hammering as we bounce in wrist-shaking, buttock-destroying tremors along pitted paths, treacherous ditches and muddy fields to arrive in the town of Tam Coc at 4pm where we eventually pull into the Hidden Charm Hotel.

I’ve got a few hours until the Truants arrive so decide to treat myself to a massage ahead of three days of pain. The hotel boasts about its spa, with posters in the lift showing a woman lying asleep with hot stones on her back and orchids surrounding her, so I’m looking forward to a similarly Zen experience. However what happens next is anything but.

Eventually we pull into the small village of Duc where hundreds of little rowing boats are moored. In a few day’s time they will be teeming with tens of thousands of pilgrim heading to the Perfume Pagodas, to celebrate Tet and pray for good fortune for the year ahead, but on this cold, and rainy day Sunny and I are the only ones mad enough to hire one of them and disappear into the mist ahead.

It’s Sunday morning and Sunny is waiting for me in the lobby after breakfast to drive through the French Quarter to the most revered shrine in the country, the gargantuan Ho Chi Minh Mausoleum. Often there are thousands of people queuing for hours to go through the X-ray machines and security checks to pay their respects to Uncle Ho, but today we breeze through in minutes, following the prescribed route past young soldiers in white uniforms, stood rigidly to attention, with bayonets affixed to their guns.

We board a motorised boat, with a stern but smiley woman at the helm, and set off down a tributary towards the lake. At first the banks are full of houses with huge beams raising them high above the waters, but Nak explains the lake is very low at this time of year, in fact much lower than it should be due to a combination of China damming the Mekong further north and climate change bringing longer than usual seasonal droughts.

The rain has eased to a light drizzle by the time I head out, and it’s only a five minute walk to the centrepiece of Hanoi, Ho Hoan Kiem, the Lake of the Restored Sword. The whole area around it is pedestrianised at weekends and as I circumnavigate it, I pass groups of teenagers on the streets dancing, shooting videos, roller skating and generally having fun. Older couples promenade arm in arm and families with toddlers on little bikes or in motorised toy cars crowd the streets, along with a number of European tourists.

Our destination is the temple of Banteay Srei, and we’re amongst the very first visitors of the day, getting to experience its splendours in the early morning light. Often referred to as the Painted Lady temple, or the Citadel of Women, its beautiful pink sandstone is delicately carved making it one of the most intricate and gorgeously decorated temples in the region, a real jewel in the crown of Angkor.

We’re taken first to the huge moat in front of Angkor Wat’s most famous temple, where we sit at the water’s edge, our eyes acclimatising to the pitch black night. We’re amongst the first to be here and it feels like quite a long wait until around 6am the dawn light starts to slowly illuminate the silhouette before us. Quiet music drifts towards us as crowds start to gather, and within twenty minutes the surface of the moat is alive with insects, frogs and dragonflies rippling across the water.

After 30 minutes gliding through back streets and down dual carriage-ways we pull up outside Ba Thien Hau Temple, more colloquially known as the Sea Goddess Temple due to the carvings on the roof. It’s a fabulous space, full of incense and altars, paintings of the twelve characters of the Chinese horoscope and, rather strangely, beautiful young women in full traditional dress conducting their own personal photoshoots.

Not as delighted as we are when we enter the incredibly luxurious suite on the 19th floor, complete with enormous bed gazing out of full-length windows over an amazing panorama of the city, just as the sun is warmly starting to set in front of us. The suite also includes an incredible open bathroom with a fabulous roll-top bath. Sometimes it pays to stand your ground!

My Son means Beautiful Mountain and is about 50km west from Hoi An. A collection of Hindu temples built by the Champa kingdom, they are similar in style to Cambodia’s iconic complex at Angkor Wat but much smaller, and at 1300 years old, much, much older. It takes about an hour to reach them, our coach weaving through rural scenes, before we disembark and grab a cold coffee with fresh coconut at the little café by the entrance.

However beautiful Hoi An is during the day, at night-time it really is like the most bewitching film-set on earth. And the best way to get around it is on bicycles. Our hotel has racks of them lined up in the entrance drive, so each night we unlock a couple and venture off into the Old Town to visit restaurants and cycle the streets, taking in the pretty lanterns that light up the bridges, boats, balconies and buildings.

There really are two different Hoi An’s, we discover. The town in daytime is a completely different affair to its night-time counterpart. The bustling streets of yellow buildings, intriguing museums, elaborate temples, pretty riverfronts and winding markets are transformed in the evening into an Oriental fairy-land of multi-coloured illuminations that create an almost dream-like neverland of bars and restaurants.

At the top, the Hai Van Pass is marked by ancient guard towers that denoted the old borders between the Vietnamese Kingdom in the north and the Champa Kingdom of the south – which also included parts of Cambodia. Later it formed part of the Demilitarized Zone that separated the communist north from the westernised south, and the towers are studded with bullet holes, which testify to the fierce fighting between the US forces and the Viet Cong.

In front us lies the Thai Hoa or Palace of Supreme Harmony, surrounded by bare frangipani trees, their leaves and blossoms waiting for winter to end and spring to bloom. Before we enter the palace to view its huge and ornate interior, we cross the large courtyard where officials would gather to hear the King’s proclamations. He would remain inside so he could not be attacked, with an official relating his words to the courtiers and passing their requests back.

Four nerve-jangling hours later – which includes a roadside toilet break at a shack with a hole in the ground and a bemused lady owner – and we arrive at the Cu Chi Tunnels just after 2.30pm, grabbing an on-the-go lunch of spicy crisps and coco-cola from the gift shop at the entrance. Tai speeds us through the ticket barriers and down a long underpass before we emerge into a forest clearing, recreated for a guerrilla encampment.

This time we jump on bikes and have a fun cycle through fields and villages, past temples and through gorgeous flowers and scenery. Trang waits by the tender for myself and Coman to return and then gets us back to the ship ahead of the others so we get a chance to experience an absolutely spectacular sunset as the golden orb sinks into the water through the silhouetted palm trees, sipping cocktails before everyone else gets back on board. It’s a proper Mekong moment.

On we go, taking in the corrugated Iron shacks whose roofs are thatched with leaves from the abundant coconut and banana trees. The hot, humid, tropical scenes, sound-tracked by exotic bird songs, ensure that the afternoon drifts along at a gentle pace, a bucolic and soporific experience that soon has Coman snoozing in the lounge while I take photos and write notes of all that we see.

I’m looking for the fabled durian fruit which apparently tastes like heaven but smells like hell. Its pungent aroma is banned in places like Singapore as the stench is so putrid, but its flesh is supposedly a delicious custard-like thing of beauty. Sadly there are none to be found anywhere but in amongst the various exotic things on offer we do see dried frogs on sticks being sold as breakfast snacks. Not ones for us…

Our route takes us on a circle around the mountain, passing through villages and countryside, with school children waving at us and roadside vendors looking on in bemusement. Communist monuments and temples and pagodas dot the landscape and we investigate a few as we go, dodging potholes and traffic, and cycling past farms and a few rice paddies.

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.

In the heart of Phnom Penh, overlooking the Tonlé Sap river is the complex of temples and palaces known as the Royal Citadel. Despite the horrors inflicted on the country by Pol Pot and the Khmer Rouge a few decades ago - and which we are soon to see in grisly detail - the Royal Citadel survived and is home once more to the revered royal family.

The streets of Phnom Penh are aglow. Neon and lasers flash across the sky, trees cascade down with multi-coloured lights, buildings, statues and shrines are bathed in illuminations that twinkle and flash. The Pearl of Asia, as the city was known during colonial times, has transcended its traumatic recent history and become a modern metropolis on the banks of the Mekong.