It takes clear water, when watching the glide of a swan, to glimpse the webbed feet paddling below the surface. China’s political waters are almost as murky as its polluted rivers. The official message that emerged from the choreographed five-yearly Communist Party congress that has just ended was of cautious, incremental reform under Hu Jintao’s oblique leadership. But that steady-as-she-goes presentation masks the intensity of the arguments raging within the party about how to tackle the social and environmental costs of the country’s extraordinary economic growth.

The new Politburo line-up may indeed force caution on Mr Hu, and his more instinctively radical Prime Minister, Wen Jiabao. At best, Mr Hu scored a draw, not a win, in the tense political jostling for the top party positions. He proved unable to clear the deck of some key protégés of his predecessor, Jiang Zemin. And he was unable to articulate a policy direction that was clearly his own or display a style of leadership that was a departure from the constraints of the past.

Strikingly, Mr Hu failed to manoeuvre his own man, the outsider Li Keqiang, whose experience lies in wrestling with the problems of China’s poorer regions, into pole position as his presumptive heir. That honour went to the business-friendly “princeling” boss of booming Shanghai, Xi Jingping. There are no fewer than seven of these “princelings”, the privileged offspring of revolutionary leaders, in the new Politburo, which Mr Hu declares will “unswervingly” promote greater equity and more rounded growth through a “people-centred approach”. China’s nouveaux riches businessmen-bureaucrats will fight their corner tenaciously, and they have plenty of friends in the new court. Few of China’s least privileged, its farmers and urban migrants, will conclude that Mr Hu’s repeated invocation of a “harmonious society” will make much impact on their struggles to make ends meet.

Yet there was more meat in Mr Hu’s interminable conference speech than many commentators have acknowledged, and both he and Mr Wen spent much of the congress lecturing the cadres that putting China on a more socially and environmentally sustainable course is not a choice, but an imperative. His campaign for reform, initiated in June in a speech attended by the entire standing committee to underline its importance, tellingly revives Deng Xiaoping’s demand in 1978 for a party-wide “emancipation of the mind”.

That phrase heralded Deng’s jettisoning of the command economy and the start of market-based reforms. The cadres are on notice that the party is at an equally important crossroads today: there must be “a fundamental change in the status quo” to spread the benefits of growth, provide decent education and social services and harness China’s “undeveloped productive forces”. The announcement, just before the party congress, that the vaunted Three Gorges dam is on the brink of “environmental catastrophe” dramatised the new emphasis on “scientific”, meaning sustainable, development. Ossified thinking, Deng said, “will destroy the party and subjugate the nation”. Mr Hu, lacking Deng’s authority, has borrowed his words to make the same point — and with the same purpose of preserving party control. But if the party does not balance economic growth with continuing reform, control will be beyond its means.