It's the kind of reaction for which the usual host of Commercial Radio's Teacup in a Storm, the abrasive Albert Cheng King-hon, is famed. Here was the former head of the Democratic Alliance for Betterment of Hong Kong, Tsang Yok-sing, getting a tongue-lashing after calling up the daily talk show to complain about its alleged anti-DAB stance. Tsang hung up - he later said he'd merely been in a hurry.

But his sparring partner this time wasn't Cheng - it was his protege Peter Lam Yuk-wah, the new hardman of the airwaves who slipped into the hotseat after Cheng quit over alleged intimidation because of his outspokenness. And today, it will be Lam who'll take Teacup onto the streets of Hong Kong, to gauge the views of some of the thousands of people who are expected to march to mark the seventh anniversary of the handover.

Lam has big shoes to fill, not least because of the size of Cheng's personality. For many, the host of Teacup is seen as the conduit through which freedom of speech in Hong Kong passes.

The show caused a storm of its own during a fortnight in May, when Cheng - known as 'Taipan' - became the first of three radio talk show hosts to quit.

On May 3, Cheng walked away, citing death threats and intimidation by 'influential people' aiming to stifle pro-democracy voices. He was followed, 10 days later, by Commercial Radio colleague Raymond Wong Yuk-man, known for his anti-communist stance.

Cheng's replacement, then-member of the National People's Congress Allen Lee Peng-fei, quit Teacup six days later, saying he felt under pressure after he received a call from a retired mainland state official who spoke to him about his family, and said he wanted to talk about the show.

Until then, the 54-year-old Lam had had played a small, supplementary role on Teacup for nearly 10 years.

But from May 19, some people might say the softly spoken and relatively unknown Lam was left holding the mantle of Hong Kong's freedom of speech.

'I feel a lot of pressure of expectation,' Lam says. 'During Taipan's absence, I feel I have to continue the show, to not let the ratings drop and to keep the programme the same. People are expecting me to keep the show's style and spirit. Before, I was supplemental to the show. Taipan did most of the talking. Now, it's up to me to keep up with the pulse of society.'

Lam, who is helped by young co-host, Leung Man-tao, has been accused of putting on an act rather than genuinely feeling passionate about the issues he raises on the show. He says that, to some extent, being angry and outspoken isn't a reflection of his true personality.

'I'm not really like that,' he says. 'When people get older, they don't want to change. When Taipan was here, he led the show. I sometimes said something witty and interesting. That is the true me. That's what I enjoy.'

Lam was born the second of five children in Shantou, in Guangdong. He came to Hong Kong when his mother and his siblings fled the Communist government. His father followed soon after. They lived with their grandparents, an uncle and his family in a squatter hut in Yuen Long, where they raised chickens and ducks for a living.

As a secondary student, Lam contributed articles on school life and music to Chinese Student Weekly. He studied journalism at the then-Baptist College (now Hong Kong Baptist University), and covered many social issues in his free time for the magazine. He quit two months before he was due to graduate, after the faculty head told him to repeat a year when he failed to submit an assignment on time, because he was sick, he says. He also quit his first job, as a reporter at the Hong Kong Standard, saying the paper wanted to reduce his salary.

Various jobs in the media followed, including a stint as a reporter on the now-defunct evening edition of Ming Pao and as a researcher for Radio Television Hong Kong's popular drama Below the Lion Rock. In 1978, while working as a research manager for the new Commercial Television, he was convicted with several others of organising an illegal assembly, after leading protests against the government's forced closure of the station.

He first met Cheng in 1983, when the pair were involved in planning a Sam Hui concert in America. Later, Lam suggested Cheng produce a Chinese edition of Playboy, which he did, before opening Capital magazine. In 1995, when Cheng agreed to host a new talk show called Teacup in a Storm, which would discuss issues of the day and help people express their opinions and voice their concerns, he brought Lam on board.

Looking back, Lam says he never minded being in the minor role. 'As in films, there must be side roles,' he says. 'Not everyone can be the star. We are good friends. I enjoyed doing the show with him. I didn't treat it as a job, but more as a chat with an old friend every morning. Even though he sometimes made fun of me, he was just trying to make the show humorous and relaxed.'

Together, the two 'self-appointed social workers' helped monitor the government on behalf of the public, fighting against injustice and inequality, and championing freedom of speech - something many in the community saw as in doubt after the departure of Cheng, Wong and Lee.

In one of his rare appearances in the Commercial Radio offices recently, a tired-looking Cheng says freedom of speech in Hong Kong is under threat. Lam, too, is concerned, saying many local media groups have changed their stance to appease Beijing. Lam knows he's now viewed as a barometer of such change.

Media commentator To Yiu-ming, an assistant journalism professor at the Baptist University, says Lam's new role is important. 'If he doesn't speak out, people might think the show's standards have fallen,' To says. 'People in Beijing may take advantage of it. His is a watchdog role, a defender of core values.'

It's a role that has put too much pressure on some of Lam's colleagues, and which worries his wife, Angela Yu Mei-ling. 'He has more pressure, these days, and can't sleep at times,' she says. 'I'm worried about his safety, and always ask him not to be so fierce in his criticism, and not to mention his family, such as where his son studies. I have asked him not to do this job, but he refused to listen.'

Lam is learning to live with the pressure. 'I'm not as strong in my political views as Taipan. They usually go after the big figures, and I'm just a small figure behind the scenes,' says Lam, who says he's only once received a threatening letter, many years ago.

From their small studio in Kowloon Tong, the Teacup team is busy taking phone calls, contacting officials and enthusiastically debating issues. Executive producer Lo Ho-wing constantly reminds the hosts of important issues through an intercom.

When Leung is talking, Lam looks calm and relaxed, and writes down points a caller makes for reference when it's his turn to speak. Today, Lam is urging the Home Affairs Department to switch on air conditioning in community centres, where people can take refuge from the heat. He also asks the Highways Department to replace its old drainage intakes to reduce the number of mosquitoes. Later, he turns his attention to the Agriculture, Fisheries and Conservation Department, urging them to let Kam Ying, a pet monkey of the late hawker Chan Yat-biu, with his son.

How long Lam remains in the limelight depends on Cheng, who has said his absence would last only until the end of the year. But his return is far from certain.

'We've been together for 10 years,' says Lam. 'I've never thought of doing this show indefinitely. If he doesn't return, I will have to think of my career path. Maybe it is god's will that I should leave. Until then, I say things I think Taipan would normally say. People say I have his ghost in me, but I just want to keep our show's standpoints until he comes back.'