'All yellow taxi drivers are Cantonese speaking,' Wu says. 'Red ones mostly Cantonese, blue and green ones mostly Putonghua.'

Like today's Hongkongers, the people of Guangzhou have long considered themselves as being apart from the rest of the country - 'The mountains are high and the emperor is far away' is a Cantonese saying that refers to the freedom the south has enjoyed by being distant from the politics of the north - with the Cantonese dialect being at the core of their sense of self.

This autonomous, defiant spirit has been fostered over centuries. Three-hundred years ago, the city was the only one in China open to Western traders. In 1900, when foreigners were being killed during the Boxer Rebellion, Guangdong declared neutrality. The 1911 revolution, which ended 2,000 years of dynastic cycles, was engineered by Sun Yat-sen, a Cantonese. The 1925 northern expedition that united the divided mainland started in Guangzhou. For 10 years during the Cultural Revolution, the biannual Canton Trade Fair was the only forum at which foreigners could do business in the mainland. And, when the mainland began opening up in the late 1970s, Shenzhen and Guangzhou were where the experiment began.

Hong Kong has played an important part, too, providing a safe harbour for Cantonese through the darkest days of communist rule and helping propagate, through its emigrants, the dialect and traditions around the world; according to the People's Daily, the Communist Party's mouthpiece, 67 million people speak Cantonese and it is the third-most spoken 'language' in the United States.

In the 70s, Li Gongming was a Guangzhou teenager with a penchant for Hong Kong radio broadcasts.

'The whole country was living under a unified political atmosphere,' says Li, a pro- fessor at the Guangzhou Academy of Fine Arts. 'Listening to Hong Kong radio and popular songs was, of course, seen as heret- ical and forbidden.'

Back then, Cantonese dialect and traditions were under threat from the Smash the Four Olds (customs, culture, habits and ideas) campaign. Today their enemy is economic.

CANTONESE SPEAKERS constitute about half of Guangzhou's 14 million population, according to recent research. The other half is classed as Putonghua-speaking; mainly people who have migrated from across China.

'There are more Putonghua speakers in Guangzhou than ever before,' says Professor Ching May Bo, of Sun Yat-sen University's history faculty. 'All levels of education, for example, are limited to Putonghua only.'

Ching, a Hong Kong native, believes it is not just the dialect that is at stake, but also a culture.

'Look at the demolition of those historic buildings in the distinctive Cantonese style, one after another,' she says. 'The facelift of the city is quite extensive and little has been done to preserve the Guangzhou character.'

Hong Kong has suffered from the wrecking ball, too, of course, 'but that was done by Hong Kong's own officials, whereas the decision-makers [in Guangzhou] are Putonghua-speaking leaders from the north who execute changes according to their own culture', says Ching. 'That is against the time-honoured policy of respect for and preservation of local cultures.'

Language has long been used by ruling elites to bring a populace into line. After fleeing to Taiwan in 1949, for instance, the Kuomintang suppressed for decades the use of Hakka, Minnan (widely spoken in Fujian province) and aboriginal dialects in favour of Mandarin (or Putonghua, as the mainland calls it). But as young Taiwanese developed a sense of identity in the late 80s, Minnan underwent a revival.

The Shanghainese seem to have found it easy to accept Putonghua while maintaining their own dialect.

'I think the Shanghai dialect itself makes it easier to grasp standard Putonghua than does Cantonese,' says Wei Wei, a Hong Kong-based Shanghainese. 'After all, Shanghai people are good in languages and Putonghua took root there far earlier than it did in Guangzhou.'

Wei believes the country's preferential policy towards Shanghai may have made a difference, too. Former president Jiang Zemin and former premier Zhu Rongji, for example, were both Shanghai officials before promotion to the top.

'As the language [of officialdom], Putonghua by necessity contains lots of rhetorical terms and expressions, and that affects the thinking process,' says Yu Yiwei, a multilinguist and Guangzhou-based columnist who has fol- lowed the issues of language and society for decades. 'That is why Cantonese has livelier expressions and its users are generally freer in their thinking.'

Despite that, Yu's three-year-old son speaks Putonghua and not Cantonese.

'My wife speaks Putonghua and my family, in Meizhou, Guangdong province, speak Hakka. So Putonghua becomes a common medium for all parties,' he says.

Wei Wei's father, Wei Zhiming, 58, a high-school graduate who was sent from Shanghai to remote Yunnan province during the Cultural Revolution, has felt at home in Guangzhou since he and his family moved there in 1992.

'My wife and I don't speak Cantonese but we have no problem understanding it. Guangzhou people ... shift to Putonghua as soon as they realise we don't speak it.'

Wei says his daughter was four when she arrived in Guangzhou, and picked up Cantonese at school. She now speaks Putonghua and Cantonese fluently, as well as English, Shanghainese and the Yunnan dialect.

'I find Guangzhou people very receptive to people and ideas from the outside, and they are very proud about that,' Wei Zhiming says. 'Over the 18 years I have lived here, I have witnessed their efforts in talking in Putonghua and they have made big progress in mastering it while holding on to their own Cantonese.'

Shan Liucai, a 30-year-old Henan native who moved to Guangzhou 11 years ago in search of better prospects, sees the situation differently.

'I don't like Cantonese. It's only a dialect. There is no point in learning it as Guangzhou constitutes less than 10 per cent of my business,' says the smart-card manufacturer. 'Even my Guangzhou clients speak to me in Putonghua, so there is absolutely no incentive to learn or to speak Cantonese.'

Shan's wife is six months pregnant. The child will be brought up to speak Putonghua - chosen by the State Council in February 1956 to be the official tongue of the mainland.

'They need Putonghua and foreign languages. My kids will learn English for sure. I don't think they need any dialect for them to do business in the future.'

The influx of Putonghua speakers into the region is not new but 'Cantonese speakers used to look down on the Putonghua folks - now it's the other way round', Yu says. 'I think this trend will go on and won't be reversed again. Cantonese folks can only hope to slow it down.'

Lu Yi, curator at the Zhan Tianyou Memorial Museum, laments the destruction of her neighbourhood, Xi Guan, a once prosperous East-West meeting point akin to Tsim Sha Tsui: 'We are the oppressed, looking helplessly at the withering of our culture. When you come to Guangzhou, it's only natural you speak Cantonese, just like you'll speak English when you go to the United States. You wouldn't expect people to speak Putonghua there, would you?'

The fact that a visitor to the US is not expected to speak Native American Navajo or Siuslaw is perhaps an example of cultural annihilation Lu did not intend to give.

YU IDENTIFIES THE late 90s as being the point at which Guangzhou's status began to diminish, leaving the city's culture vulnerable to erosion.

'The Asian financial crisis was the turning point and Guangzhou has yet to recover from it. By contrast, China as a nation soared after joining the World Trade Organisation in 2001. Since then, Putonghua has become a symbol of the elite, and Cantonese a waning dialect.'

Guo Weiqing, professor of the school of government at Sun Yat-sen University, agrees: 'Guangzhou benefited from the decentralising policy of the 80s. It was the conduit through which Hong Kong trade and culture extended to all parts of China. The liberal policy bred private enterprises, which mushroomed and prospered. But it all changed in the 90s, when power was centralised again through policies such as tax and planning. Large state corporations took charge and that dealt a hard blow to the Guangzhou enterprises.'

The Guangzhou-born professor is pessimistic about the future of Cantonese but has not given up hope: 'I observed the July 25 rally. What struck me most was the many young faces, from the post-80 and post-90 generations, taking to the streets to defend Cantonese. That really shows the character of Guangzhou as a maturing civil society that embraces freedom and diverse cultures. They genuinely believe their core value is under threat and they express their concern.'

The professor says there have been other examples of civic pride recently. Public campaigns scuppered the government's plan to build a rubbish-disposal plant in Panyu and saved the 270-year-old Tianzi Pier, located on the northern bank of Pearl River. This act of public activism, which occurred in 2008, is recognised as the city's first civil movement to conserve its cultural heritage.

Inspired by the campaign to save Central's Star Ferry and Queen's piers, thousands of citizens flooded internet discussion forums to express dismay at the government's decision to demolish Tianzi Pier to make way for a tourist attraction for the Asian Games.

'After seeing the efforts of Hong Kong people to save their piers, which are not as old as ours in Guangzhou, we believed it was our civic duty to save our heritage for future generations,' says Deng Xiaoying, 24, a teacher and volunteer conservation worker.

In response to these efforts, the city government abandoned the plan to pull down the pier. The defenders of local culture were ready for greater battles: the summer rallies. The trigger came on July 5, when a member of the Guangzhou advisory body submitted a proposal to change the city's prime-time television programmes from Cantonese to Putonghua, to benefit visitors to the Asian Games, to be held in November.

'It's sheer stupidity, period. I don't know where it will take us in the end,' sighs Guo.

The rallies could not have come soon enough, says Yuan Xinting, a former editor with state-run Guangzhou Publishing House.

'It is the best civil education one could hope for,' he says. 'We have watched a lot of Hong Kong news and documentaries about citizens exercising and defending their rights. This time we did it on our own. It is a wake-up call for many. The July 25 rally is to us a renaissance of Cantonese. It could be an important date to remember.

'I support the movement because it's not just about Cantonese,' says Yuan, a Sichuanese who arrived in Guangzhou in 1998 and even now can speak the local dialect only haltingly. 'It's about a fight against the abuse of public power, which in this case is being used to smother cultural diversity.'

Yuan says he was fired two weeks after the second rally, when hundreds gathered in a city park in defiance of a government order not to. He was accused of 'instigating riots' and used in evidence were text messages urging people to 'take a walk' that he sent from his cellphone, which was hacked into.

'I have no regrets and I will keep pursuing what I believe in. The rallies give me hope in the new generations, who, unlike us, did not experience the June 4 crackdown in 1989 and the aftermath.

'They have the cleanest soul and stand up for their rights without hesitancy.'

Lang Zi, a Guangzhou poet who also took part in the rallies, says: 'The loss of a dialect is the loss of one's home, one's culture and one's identity. That is what we are defending.'

The future of Cantonese, he adds, lies in the hands of the people of Guangzhou. 'Only a civil society can help us. In other words, we need to help ourselves.'

Yu says: 'A dialect like Cantonese can only be safe when China embraces democracy.

'Take a look at Taiwan. When Taiwan carries out direct elections, even a local dialect becomes the official language.' (President Chen Shui-bian spoke Minnan on many public and official occasions when in office).

But Guo looks at Cantonese beyond the dialect level: 'I think Cantonese represents tolerance, freedom and diversity, and all that forms the framework of a civil society. What it is facing is not just Putonghua but a strong central government and its superimposing ideology. It is in that sense that Cantonese needs to be safeguarded.'

Others have more fire in their belly. 'We've put up with too much for too long,' says Michelle Xie, a 21-year-old who came from Guangzhou to participate in last month's rally in Hong Kong. 'We've got to fight for what is ours.'

Additional reporting by Verna Yu