The drama that has unfolded since spy-cum-whistle blower Edward Snowden arrived in Hong Kong in June continues to create shock waves around the world. It's a story that has all the ingredients of a best-selling espionage novel.

The Snowden affair is, in fact, reminiscent of an even more sensational story involving a political outcast pursued by the secret agents of a superpower. Set at the turn of the 20th century, when Hong Kong was a hotbed of revolution, insurrection and intrigue, this is the tale of a high-profile revolutionary leader who was assassinated on the streets of our city and then air-brushed out of the history books.

The assassination was brought to life on the big screen by director Teddy Chen Tak-sum in the 2009 award-winning blockbuster Bodyguards and Assassins. The movie's opening scene - set on a sunny day in Gage Street, Central - sees a teacher descend iron steps from the first floor of a colonnaded building, surrounded by attentive Chinese students. As he talks to them of democracy, a gunshot rings out and a bullet pierces the teacher's forehead, spraying blood onto the faces of his shocked companions. Panic ensues as the camera zooms in on the sinister face of the assassin, still peering down the barrel of his bolt-action rifle on a nearby rooftop.

This is the murder of Yeung Ku-wan, the leader of the Xing Zhong Hui (Revive China Society), and the date is January 10, 1901.

Despite playing a leading role in the early days of China's republican revolution, which was largely orchestrated from Hong Kong, and being immortalised by popular cinema, Yeung has faded into the background in comparison with Sun Yat-sen, the "father of the nation", when it comes to the story of the long struggle towards the formation of the Chinese republic in 1911.

A flick through the Dictionary of Hong Kong Biography reveals that "Yeung Ku-wan is considered a hero of China's republican revolution, not least because he gave his life for it". It also tells us that Yeung formed the Furen Wenshe (Literary Society for the Promotion of Benevolence) in Hong Kong in 1892 with close friend Tse Tsan-tai, who would become one of the founders of the South China Morning Post.

Initially, the society campaigned for modern reforms in China but quickly developed into a secret organisation focused on fundraising for and organising armed insurrections. Its members plotted to overthrow what they saw as an obsolete and corrupt Qing dynasty and replace it with a modern democratic republic. Yeung became a close ally of Sun after Furen Wenshe was merged, in 1895, with the Revive China Society - which Sun had founded - at the latter's request.

Born in Dongguan, Guangdong province, to parents who were natives of Haicheng, Fujian province, Yeung came to Hong Kong as a boy and graduated from St Paul's College. After a short time working at the naval dockyard, where he lost three fingers in an industrial accident, he developed close connections with the local Chinese business elite as an influential comprador for leading shipping companies such as Sassoon & Company.

His experiences in Hong Kong aroused his political instincts and he began to develop a fierce nationalism.

Hero of the revolution and one of the most influential Hongkongers in Chinese history though he may have been, for more than 100 years after his death there was little mention of Yeung, in his home city or anywhere else. There were no streets named after him, no statue and no obvious legacy - just an unmarked grave in the shady upper levels of the cemetery in Happy Valley, with only the tombs of British servicemen and swarms of mosquitoes for company.

In 2011, after a long campaign by historians and family members, a modest marble plinth was erected next to Yeung's grave - which had been left unmarked at his own request, to deter Qing vandals - telling the story of his life and his role in history. One of those campaigning family members was Yeung's great-nephew, Albert Yeung Hing-on, an erudite and softly spoken scholar of Chinese literature who lives in Hong Kong and spent more than 10 years researching a book about the life of his relative.

"My father maintained a detailed family history," says Yeung. Referring to evidence contained in his book, He explains his theory that his great-uncle has been deliberately sidelined in the official history of the republic. He points out that when Sun and Yeung Ku-wan merged their organisations, it was the latter who was appointed chairman of the influential new group.

"Dr Sun was not in Hong Kong, so he had no power, no money and no connections - it was Yeung Ku-wan who had the local influence. Yeung was also five years his senior," says Albert Yeung.

You can visit the small park in Pak Tse Lane in Central where Yeung Ku-wan's secret society was formed. A memorial has now been installed there - complementing an existing one nearby, at the site of his assassination; both are part of the Sun Yat-sen Historical Trail. The covered alleyway leading to the park from Gage Street, with its stained walls and strewn rubbish sacks, is easily overlooked but it would still make a great location for a clandestine political rendezvous some 120 years later. It was here that the plotting would have taken place for the 1895 uprising - the first of the revolutionary campaign - and Albert Yeung shows me a group photograph of the Furen Wenshe. The caption on it, which clearly shows the date as 1890, contradicts the history books, which state the organisation was formed two years later.

"So there were maybe three years of planning, networking and sourcing munitions before Sun even met Yeung Ku-wan [in 1894]," says Albert Yeung.

The 1895 armed uprising planned for Canton (Guangzhou) by the two revolutionaries ended in a shambles with Sun's closest friend, Lu Hao-tung, being captured and tortured to death. Significantly, though, it meant the word "revolution" was being whispered for the first time in relation to Qing-dynasty China. It also resulted in both leaders becoming wanted men with a price on their heads.

A diplomatic crisis erupted as a furious China accused London of what we might now call "harbouring terrorists" in Hong Kong and, rather than wait around for an extradition order, both leaders left town.

Sun and Yeung were reunited in Japan in 1898, where they both lived in exile. The official history records that Sun took over as head of the movement after a major falling out with his former ally, who then fades into the background.

Albert Yeung disputes this account, however, and points to the significance of a group photograph taken in Yokohama in 1898: the two young revolutionaries, both in Western attire, are pictured together with influential Japanese. Yeung Ku-wan sits in a prominent position in the front row while Sun is at the back. Albert Yeung makes the astonishing claim that years after his great-uncle's death, the leader of republican China, Chiang Kai-shek, tried to obtain the picture.

"Chiang Kai-shek's second wife claimed that her husband offered a huge sum to obtain this photo as he feared it would degrade the status of Sun Yat-sen," he says.

He also denies there was ever a rift or falling out between the two men. Albert Yeung relates his father's account that, when they were both in Japan, Yeung Ku-wan asked Sun, who had a medical background, to supervise the birth of his youngest daughter and that years later, in February 1923, when Sun returned here to address the University of Hong Kong, he contacted Yeung's wife and asked her to visit him.

"They remained firm friends throughout," says Albert Yeung.

Indeed, far from fading into the background, Yeung has found evidence that his great-uncle was instrumental in the more sustained but ultimately futile second uprising, in 1900, which was again orchestrated from Hong Kong. The signed confession of revolutionary Shi Jianru, who was beheaded for his attempted assassination of the governor general of Guangdong, directly implicated Yeung Ku-wan in the plot.

"Sun left after the 1900 uprising but Yeung was more reluctant, having a wife and four children and having already spent years in exile," says Albert Yeung.

Yeung Ku-wan stayed in Hong Kong with his family, teaching English in Gage Street, presumably with half the assassins of southern China (sponsored by the Qing secret service) searching for him.

He paid for that decision with his life. He was gunned down in the first-floor classroom at his Gage Street home - not exactly how it was portrayed in Chen's movie. He tried to protect himself with an English dictionary while reaching for his own pistol but was wounded and died in hospital the next day. Strangely, the official police report for 1901 is restricted to 2½ lines - and mistakenly gives Yeung's age as 84 - even though there were only four murders in the city that year.

"My father always said it was a personal vendetta, not a political assassination," says Albert Yeung.

The memorial near the site of Yeung Ku-wan's murder - just south of Gage Street, in an alleyway adjoining Aberdeen Street - comprises a simple red plaque that has been upstaged by colourful graffiti nearby.

The recent inclusion of Yeung's story on the heritage trail and the new memorial for the Furen Wenshe are largely due to the work of historian Joseph Ting Sun-pao, who was chief curator of the Hong Kong Museum of History and oversaw the establishment of the Dr Sun Yat-sen Museum before his retirement in December 2006.

Ting retains a boyish enthusiasm for his favourite subject and still finds time to teach history at Chinese University, be a member of the Antiquities Advisory Board and conduct his own independent research into the Chinese revolution. If anyone can make sense of the family theories and the reason for Yeung's century of invisibility, he can.

"The reason Yeung Ku-wan is low profile is very political," he says, with a slightly mischievous smile, explaining that a clue could be found many years later in post-revolution China. When Chiang took over leadership of the ruling Kuomintang party following Sun's death, in 1925, he badly needed credibility, so portrayed himself as the true and legitimate successor.

"If Sun Yat-sen became a saint, then Chiang Kai-shek could be at least half a saint," says Ting, "so he deliberately played down the importance of any associates of Dr Sun in the official party history."

So could this support Albert Yeung's claim that Chiang tried to pur-chase the Yokohama photograph in order to airbrush his great-uncle out of history?

"At first I was very doubtful about this," says Ting, "but the claim was indeed made in a book written by Chiang Kai-shek's second wife."

Ting also located evidence in Taiwan that revealed that once the Chinese republic had been established, Tse and some of Yeung Ku-wan's other colleagues made a formal request for his body to be removed from Hong Kong to its rightful place in the revolutionary cemetery in Guangzhou. Ting found official documents that showed the request was eventually refused on the grounds that the revolutionary's "stance against the Qing had wavered" during the 1900 uprising.

"From this point, when Yeung Ku-wan is accused of betraying the republic, he was successfully marginalised," says Ting.

So is Albert Yeung justified in claiming that his great-uncle had a much more significant role in the early stages of the revolution than the history books would have us believe?

"All the funds came through Yeung Ku-wan and he had all the connections," says Ting. "I agree that [he] had a more important role in the very early days of the revolution than Sun Yat-sen, who was [then] just a young medical graduate."

It seems, then, that it was Yeung and not Sun who initiated the republican revolution and instigated the first uprisings against the Qing. Even today, the faintest of possibilities that the true father of the Chinese revolution might have been a Hongkonger is sensitive territory, but Ting has one more shock in store.

When asked about why Yeung did not flee Hong Kong after the 1900 uprising, when his life was clearly in danger, his answer is unexpected.

"I think he was British," says Ting. "Otherwise he would not have been buried in the cemetery in Happy Valley."

It is known that the colonial authorities had issued Yeung with a firearm for his own protection and he enjoyed a close relationship with the British, but Ting believes he must also have been made a British subject, perhaps even a citizen.

That the founder and originator of the Chinese republican revolution might have been a Brit seems fantastical, but Ting just maintains a fixed smile and says nothing further.

Much like the Snowden case, the assassination of Yeung Ku-wan was the biggest news story of its day. Albert Yeung was told by someone whose grandfather attended the funeral that it was like "the death of Bruce Lee"; though given the diplomatic sensitivity, "there was only a small column in the newspaper", says Ting.

Yeung stresses he is not trying to undermine the important role of Sun as the "father of the Republic" but would just like to see recognition of his great-uncle's legacy in those early days of the revolution.

"Yeung [Ku-wan] is very important because he presented the Hong Kong spirit to find the truth and take action," he says.

Clearly neither China nor Britain had much incentive for promoting Yeung as a hero of the revolution. How welcome it is that the true story of this influential player can be better understood at last. At least in Hong Kong.