"Young men and women will hesitate before joining social movements to promote political liberalisation. This is a step back for One Country, Two Systems and a high degree of autonomy as this is a clear retrogression for democratisation,” he said.

One Country, Two Systems was the Beijing pledge when it resumed control of Hong Kong in 1997. It meant the former British colony would continue to have a high degree of autonomy.

Unlike earlier attempts by Hong Kong prosecutors to jail radical young students, such as Joshua Wong, who became the international face of the Umbrella Revolution, the latest trial targeted middle-aged, middle class professionals, said Lowy Institute analyst Ben Bland.

"This sends a very different message," he said.

Hong Kong's city centre was brought to a standstill for 79 days by the street protests, which called for universal suffrage in the election of a Hong Kong chief executive, instead of voting on a pool of candidates vetted by Beijing.

Four years after the protests ended, the trial of nine Occupy organisers is seen as part of a broader crackdown by Chief Executive Carrie Lam's government on dissent under pressure from Beijing to curb calls for greater democracy.

"I would not say it is a nail in the coffin but a sign of the growing pressure ... the price of resistance keeps rising and the chance of success keeps reducing," said Bland, the author of the book Generation HK: Seeking identity in China's Shadow.

Judge Chan said prison terms had been imposed on four defendants because of their lack of remorse.

Two sitting Legislative Council politicians have also been found guilty - Shiu Ka-chun, 49, was sentenced to eight month's jail, while Tanya Chan, 47, will be sentenced at a later date after the court was told she had a brain tumour.

Political activist Raphael Wong, 30, was sentenced to eight months in prison.

Former student leader Tommy Cheung, 25, was handed 200 hours of community service after public letters of support for his character and the judge took account of his age at the time of the protests.

Easson Chung, 26, another former student leader, received a suspended sentence.

"There was definitely a strategy, after the Occupy movement, [for the government[ to wait it out," Bland said of the delayed trials.

He said Hong Kong was experiencing a crackdown against academics, publishers and civil disobedience.

Chan said before the sentencing: "In the verdict, the judge commented that we were naive - believing that by having an Occupy movement, we can attain democracy. But what is more naive than believing in 'One Country, Two Systems'?"

The British government has watched the trial closely. Minister for Asia and the Pacific Mark Field said after the guilty verdicts on April 10: "It would be deeply concerning if the ruling discourages legitimate protest in future or discourages Hong Kong citizens from engaging in political activity."

Beijing is also watching.

The South China Morning Post reported that Beijing's top official in Hong Kong, Wang Zhimin, last week praised the guilty verdicts as drawing a red line on illegal activities that endangered social stability and called it "a momentous day for the rule of law to prevail in Hong Kong".

Hong Kong's Final Court of Appeal last year overturned the prison sentences handed to student leaders Wong, Nathan Law and Alex Chow for unlawful assembly, in an earlier trial.

Law had become Hong Kong's youngest-ever elected politician in 2016, before being disqualified for a protest during his oath-taking.