After five days promoting New Zealand's political and commercial interests at the highest levels in China, it was hardly surprising that John Key was revelling in his pas de deux with what he called the world's "biggest capitalists".

"Through foreign eyes we look at them and say they're communists, and therefore they wouldn't be capitalists, but it's quite the opposite," he confided after meeting Chinese President Hu Jintao and Premier Wen Jiabao at Beijing's Great Hall of the People.

Throughout his first official visit to China Key had been consistently 'on song' - pushing the message that when New Zealand and China signed signed their historic bilateral free-trade deal last year it opened an important door: "Now our task is to boldly walk through it."

But by the time he reached Hainan Island to take part in China's Boao Forum for Asia, Key was sufficiently pumped-up to deliver a different message to the Chinese leaders: that countries with larger financial and trade surpluses "might have to consider accepting exchange rate movements that are adverse in the short term just to get everything going again."

The subtlety of Key's message was not lost on the Boao Forum participants, who included many of Asia's top business and political power-brokers.

The Prime Minister was, after all, sharing the same stage as Wen, who used his own extensive address to the forum's opening ceremony to make the case for Asian nations to step up their economic co-operation to combat the continuing global crisis.

Key - who was global foreign exchange manager at investment bank Merrill Lynch before entering New Zealand politics - takes the view that in an interconnected financial world, the same forces that drove the credit crunch could just as quickly drive the upswing. But for that to happen, the big players - like China - need to do their part.

It was a bold call, given China's sensitivity to any suggestion that the level of its exchange rate is crippling efforts to refloat international trade.

"The Chinese were very intrigued with our new Prime Minister and his financial background," says Solid Energy's Don Elder, the sole Kiwi businessman to attend the Forum.

Earlier, Key met Zhou Xiaochuan, the Governor of the People's Bank of China, who caused a stir last month when he posted an essay on his bank's website promoting the creation of a supra-sovereign reserve currency in a direct challenge to the supremacy of the US dollar as the world's No 1 reserve currency.

Key was well aware of Zhou's agenda. But he did not get into public debate on this score. The furthest he went was to acknowledge in a formal economic speech that "serious attention" would have to be paid to the rebuilding of the international financial architecture. "In my view any repairs will have to include bigger participation for the big Asian economies, and China in particular."

Observers say the Key/Zhou meeting was not a "superficial chat" but "two experts discussing the financial crisis and China's monetary policy in considerable depth".

Says Key: "I don't see the Chinese moving to full convertibility of the renminbi any time soon."

The Boao excursion had an underlying context. This was Key's chance to get up close with some of the powerful Chinese businessmen who were also at the forum and promote New Zealand's cause as a safe haven for international investment.

China's drive to buy controlling stakes in resource-rich companies has sparked controversy, particularly in Australia and the United States.

But Key says he made the point that China was hugely under-represented as an investor in New Zealand, with just half a billion dollars of foreign direct investment compared with $50 billion of New Zealand assets in Australian hands and a combined $25 billion held by Britain and the US.

He also pushed New Zealand's case at a lunch with Zhu Yunlai, the Hong Kong-based president of China International Capital; Jiang Hong, vice-president of Sinosteel, China's second-largest iron ore company; CITIC Capital chief executive Zhang Yichen; and Captain Wei Jiafu, chief executive of major Chinese shipping firm Cosco. Some of these have already had varying experiences investing in New Zealand.

CITIC's forestry investments in the central North Island were not greatly successful, and Sinosteel Australia has run into Maori Party opposition to plans to mine ironsands on the North Island's west coast.

Key acknowledges popular opposition to China's Government-directed international buying sprees. But he says if Chinese investment is directed into "greenfields" ventures, or co-ventures with existing New Zealand players, China could give this country's economy a valuable boost at a time when the ability to source international equity is constrained.

Elder notes that if new overseas investments can be made in a way that lifts GDP, it will be much better for the New Zealand economy than simply transferring the ownership of more assets abroad.

Key met separately with Lou Jiwei, chairman of China Investment Corporation, the world's largest sovereign wealth fund, which is seriously interested in New Zealand.

Key has promised the Government will look seriously at any Chinese advances on what he calls a "case by case" basis, particularly where potential investors are willing to contribute capital, be long-term partners and help to develop New Zealand's primary resources, agriculture and forestry.

Inquiries in Beijing suggest Key's conversations with prime Chinese business leaders were seen as a very practical way of showing the New Zealand Government's willingness to welcome Chinese investment.

The word from Beijing is that the Chinese businessmen are seriously considering Key's stance.