The glorious French colonial architecture of the presidential palace in Hanoi, once the headquarters of the governor general of French Indochina, has long had a contemporary twist, with a giant bust of the Vietnamese war leader Ho Chi Minh at one end of the hall that is decorated with chandeliers, dark marble pillars and 19th-century curved windows.

There is of course the Vietnamese flag – red with a single large yellow star in the middle. But this week, standing beside it was the union jack, marking the first ever visit by a British prime minister to a country that had always been seen as a preserve of the French.

Vietnam may be one of the last five true Communist countries in the world. It maintains all the trappings of a dictatorship that tramples on human rights, but Cameron clearly thinks this is a regime with which he can do business. That said, a delicate diplomatic dance is required to handle the often opaque politics of the Vietnamese Communist leadership.

Judging by the parade in the pouring rain in front of the prime minister, the military are fiercely disciplined and numerous. Doubtless many are the sons and grandson of veterans who defeated the US army 40 years ago during the war of unification.

Cameron was only eight when the war ended, so all the leftwing protests against the Vietnam war outside the US embassy in Grosvenor Square mean nothing to him. The controversy over Harold Wilson’s decision to refuse to join America in the war – Wilson said the American president Lyndon Johnson would have been happy with a Scottish bagpipe band – largely passed him by, and No 10 was eager on Tuesday not to pass judgment on the war.

Landmarks of the war in Hanoi abound, such as the sign at the Trúc Bach lake into which US senator John McCain fell in active service as a wartime pilot. The Hỏa Lò prison colloquially known as the Hanoi Hilton, where American prisoners of war were held, is now open to tourists.

But if Hanoi’s politics have changed little in the past 40 years with Communist rule as dominant as ever, the elderly men running the country have let loose a casino capitalism. In a symbol of change, the building in the former Saigon from which US marines and CIA agents were helicoptered at the end of the war is now a luxury area selling Burberry.

Cameron travelled in Vietnam as a young backpacker in the early 90s, and despite the protocol-ridden formalities of the signing ceremonies for Rolls Royce engines and Prudential Assurance, he would find the sprawling metropolitan city quite startling with its bars and vibrant streets. The US may have lost the battle to protect south Vietnam from communism, but its capitalism may yet win the war.

Cameron is in Vietnam to get Britain access to the fastest growing middle class in south-east Asia. The statistics of economic transformation are, as Cameron said, extraordinary. The country’s growth per head was 350% between 1990 and 2010. It is currently growing by 6% a year and is predicted to be one of the 10 fastest growing economies in the world. Britain’s aid programme, not obviously necessary, comes to an end next year.

Startups burst on to the scene regularly. A third of the entire country, 30 million people, are on Facebook – 17 million via smartphones or tablets – and they are estimated to spend two and a half hours a day on the site.

Vietnam is also a young country. Two-thirds of the population was born after the fall of Saigon and the reunification of Vietnam in 1975.

There is a wider diplomatic game afoot, too. Cameron is trying to use Britain’s historical connections in places like Kuala Lumpur and Singapore to build a network of friendly south-east Asian countries that will give Britain a trade option other than China.

It is a hard call knowing whether the prime minister’s presence as a trade emissary opens door for the British. But judging by the 15 TV cameras, the signing ceremonies and full-scale diplomatic formalities, it does.

By Patrick Wintour - The Guardian - July 29, 2015