The media mogul and pro-democracy activist Jimmy Lai has gone on trial at a heavily guarded Hong Kong court on national security charges that could lead to life imprisonment. Lai’s trial, expected to last months, is one of the most high-profile prosecutions in the Hong Kong government’s crackdown on opposition, and has been widely condemned by rights groups and other governments. The 76-year-old pro-democracy activist and founder of the now-closed Apple Daily newspaper has been accused of conspiring to collude with foreign forces to endanger national security under sweeping legislation Beijing imposed on Hong Kong in 2020 and of conspiring to publish seditious material. If convicted – a prospect observers say is likely – he faces a sentence of up to life in prison. His case will be heard before three national security judges handpicked by the government. The first day of the trial adjourned without Lai having entered a plea. His legal team sought to have the sedition charges, which were brought under a colonial-era law and not the national security law, dropped for being outside a six-month statute of limitations. Lai stands accused of conspiring to print, publish, sell or distribute “seditious publications” between April 2019 and 24 June 2021, when Apple Daily’s final edition was published. Lai was charged on 28 December 2021. Lai, who has not been seen publicly since 2021, appeared in court on Monday in a suit, looking thinner than in previous appearances. He smiled and waved at the gallery where his family sat. He is also a British citizen and representatives from foreign consulates of the US, UK, Australia and Canada were present to observe the trial. About 100 people had lined up for public gallery seats before the trial at West Kowloon court began at 10am local time (0200 GMT). Some members of the public waved at Lai to show their support. Hong Kong’s Roman Catholic cardinal, Joseph Zen, a vocal democracy advocate in the city, was among those attending. Hong Kong’s security chief, Chris Tang, put in place a large police presence for the trial, in apparent anticipation of protesters, and officers had been stationed outside the court since Sunday. Civilian attenders were vastly outnumbered by officers equipped with bomb-sniffing dogs, a Chinese-made “Sabretooth” armoured vehicle, and a bomb disposal van stationed nearby. A university student from the mainland said he had been there for about an hour. He said he had read about Lai on X and was curious how the trial would go. “I think people shouldn’t be sentenced for their speech,” said the politics student, who declined to give his name. A woman in the line, who also declined to give her name, said she had been following the news about Lai closely. The retiree said she had never been to court before and did not know what to expect. The veteran activist Alexandra “Grandma” Wong was encircled by several police officers with cordon tape while across the road from the court building. She was holding a British flag, which she became well known for carrying during the protests in Hong Kong in 2019. Among those queueing were several law students from the University of Hong Kong, who said they were there to observe the trial as a study of the national security law. Lai has been in jail since December 2020 and is serving a sentence of more than five years on fraud charges for violating a lease contract, a charge his supporters say was politically motivated. In August 2020, he was arrested and later charged with the national security law violations for which he is now on trial. The UK government at the time called the charges “highly politicised”. On Sunday, the UK foreign secretary and former prime minister, David Cameron, condemned the “politically motivated prosecution” and called for Lai’s release. “Hong Kong’s national security law is a clear breach of the Sino-British joint declaration. Its continued existence and use is a demonstration of China breaking its international commitments,” Cameron said. “As a prominent and outspoken journalist and publisher, Jimmy Lai has been targeted in a clear attempt to stop the peaceful exercise of his rights to freedom of expression and association.” The US state department also condemned the trial, noting as well that Lai was denied his choice of legal counsel. It called for his release, as well as “all others imprisoned for defending their rights”. The national security law was imposed by Beijing – with the blessing of the Hong Kong government – in June 2020, in response to the previous year’s mass pro-democracy protests. Hundreds of people have since been arrested under its broad remit, which outlaws acts of sedition, secession, foreign collusion and terrorism. Critics have accused Hong Kong authorities of using it as a weapon to crush dissent. Hong Kong authorities are pushing on, unmoved. Tang has previously praised the 100% conviction rate of the national security law, and last month said the open trial of Lai would allow the public to see how “bad” his alleged offences were.