The 76-year-old took the witness stand in his trial for collusion with foreign forces, breaking the silence he has kept over five previous trials arising from his participation in the city's now quashed democracy movement.

Lai's case is one of the most prominent prosecuted under the national security law imposed by Beijing in 2020, and Western countries and rights groups have demanded his release, raising concerns over his health.

But Lai looked well and spirited on Wednesday, entering the courtroom smiling and flanked by four prison officers.

Sporting a pair of thick-rimmed glasses and a green jumper, he waved to the public gallery as he sat in the dock.

From the beginning of his testimony, the tycoon was strident, describing how he had got into the media business "to participate in delivering information, which is delivering freedom".

His outlets were "always in support" of freedom, he said, describing himself as a "businessman and social activist".

Clearly used to authority, he was almost prickly at times, such as when asked why he had retired from his media company Next Digital after 2014.

"I am the boss, if I want to retire, I can retire," he said.

But he described a deep sense of responsibility for his outlets, explaining why he made himself executive chairman of Next Digital just a month before the security law came into force.

"It's right for me to take up the responsibility of the company if anything happened to it, as an owner," he said.

- 'Radical all along' -

Throughout the day, Lai answered quickly and confidently, frequently jumping in before his defence lawyer had even finished asking a question.

Much of the afternoon was spent delving into Lai's interactions with executives of his now-shuttered Apple Daily tabloid, several of whom have testified against him.

In response to ex-Apple Daily editorial writer Yeung Ching-kee's testimony that Lai had radicalised from 2014 onwards, he was dismissive.

"I don't know how he got this impression. I rarely talked to him... If I was radical, I was radical all along."

He denied dictating editorial direction, which has been charged as being "seditious", at his outlets.

"I have a very strong personality, but do I have a very strong enforcement in my management? I don't agree," he said.

Asked whether he had made donations to US organisations to influence them into taking action against China or Hong Kong, he scoffed at the amount he had given.

"My donation is too small to be even mentioned, not to say to influence," he said, adding he had never contributed to a US political party.

Lai's wife and daughter were in court, accompanied by Cardinal Joseph Zen, one of Asia's highest-ranking Catholics who is also being investigated under the security law.

Lai, who is also Catholic, sometimes turned to look at them during his testimony, sitting just a few metres behind him.

As court adjourned for the day and he made his way out of the witness box, he waved and blew them a kiss.