In the era whose secret he uncovered, a journalist's office would have looked just like the one where Yang Jisheng works now. The tiled floor, the grimy window panes, the desk piled two feet high with papers, envelopes and books. The Mao-era radiators. The cigarette ash and the dust.
Under Mao Zedong, Yang's good fortune was to find a job as a reporter with China's state-run Xinhua news agency. His misfortune had been to see his father die of hunger in 1961, at the height of the famine that killed an estimated 36 million people:
"When my dad died, I thought it was just my family's problem. I blamed myself because I hadn't gone back home to pick wild plants to feed my dad. Later on, the governor of Hubei province said millions of people had died. I was astonished," Yang says.
In the 1990s Yang, by now a senior editor at Xinhua, used his status to secretly research the truth about the famine in 12 different provincial archives:
"I could not say I was looking for data about the famine, I could only say I was looking for data about the history of China's agriculture policy. In the data, I found a lot of information about the famine, and people who starved from it. Some of the libraries allowed me to take photocopies; some only let me write the information down. These," he gestures casually at a teetering pile of brown envelopes on the floor, "are the photocopies".
The result was Tombstone: The Untold Story of Mao's Great Famine, published in the West this year to high acclaim.
Yang, aged 72, is neat, small, swaddled in two jumpers despite the shafts of winter sunlight that stream across his desk. He is rummaging through his shelves on the hunt for a book whose title is important: by a Western author whose name has slipped his mind.
"Something about slavery?" he says. I try the name Hayek and after a bit of transliteration it works. He had stumbled on Friedrich von Hayek's The Road to Serfdom in a library and chuckles with mild scepticism when I tell him it is probably the most influential book in Western economics:
"Before I read Hayek, I had only read works the party wanted me to. Hayek says that to use the state to promote a utopia is very dangerous. In China that's exactly what they did. The utopia promoted by Marx, even though it is beautiful, it is very dangerous."
Even now, 50 years on, Chinese official history insists the famine of 1958-61 was a natural disaster. Yang's work demonstrates the famine's massive scale and its direct, political causes.
Agriculture was brutally collectivised, leaving peasants dependent on centrally distributed grain. Local cadres ordered the forced pooling of family kitchens, confiscating all ladles and punishing those who kept private food supplies.
Then, as Mao ordered rapid industrialisation during the Great Leap Forward, the grain supplies disappeared. Simultaneously local officials, terrified of failure, began to report fictional bumper harvests. Mao, meanwhile, publicly humiliated any party leader who voiced doubts. The result was the greatest famine in modern history.
It is Yang's refusal to duck the parallels with today that make his book unpublishable in mainland China. The famine happened because the party was all-powerful, he argues - just as numerous disasters visited on China by today's leaders - from the HIV-infected blood selling scandal, to the spread of Sars, to the shoddy buildings that collapsed during the Sichuan earthquake - are the result of unfree politics and an unfree press.
Despite its samizdat status, Yang thinks there may be around half a million copies of the Hong Kong edition circulating in China. His own copy, discreetly kept in a cupboard, is a black-market version of the latter: its pages are photocopied, its binding stiff, shiny and amateur.
"It is estimated that there are about 100,000 of these knock off copies in circulation," he says. "People try to bring the real ones from Hong Kong but they get confiscated, so they make these. The response is very strong, I have received lots of letters from readers telling me the stories of relatives who died from the famine."
The English language version has made a massive impact, with some calling Yang the Chinese Solzhenitsyn. To me, however, he seems more like the Chinese equivalent of Vasily Grossman: though he believes Marxism is a dangerous fantasy he remains a party member. His haunting prose - like Grossman's - defends the power of memory:
"China has undergone an enormous transformation. But… the abuses under the exclusive profit orientation of a market economy and the untrammelled power of totalitarianism have created an endless supply of injustice, exacerbating discontent among the lower class majority. In this new century I believe that rulers and ordinary citizens alike know in their hearts that the totalitarian system has reached its end." (Tombstone, p22)
What is it like, I ask, to be an historian in a country where historical memory is so completely suppressed?
"Very painful," he says. "We learn a lot about history. However, most of it is fake. It is full of made-up stories to meet the needs of ideology. Once you realise you've been cheated, you'll begin to pursue the truth. That's what I did: I've been cheated, so I want to write the truth - however risky it is."
Though retired from Xinhua, Yang is still active. The small political magazine he runs out of this tiny office seems, from piles of unsold copies stacked up in the corridors, not massively influential. He thinks it will take 10 years to publish Tombstone in the People's Republic, if the political reform process keeps to its current glacial pace.
But like all dissident writers in China, he has learned not to hurry.
He pinches green tea leaves for me into a paper cup, and pours hot water from a flask. There is a barely-touched and ancient computer in one corner of the room, but Yang's conquest has been made in the world of analogue information: photocopies and scribbled notes.
He pats the English edition contentedly, still stunned by the price the publishers Penguin are charging for each one:
"Tombstone has four layers of meaning. The first is for my father who died in the famine, another is to remember the 36 million people who died during the famine. The third layer is a tombstone for the system that killed them."
And the fourth?
"The fourth is - the book has put me at political risk, so it's a tombstone for myself if anything happens to me because of writing it."
See Paul Mason's report on Yang Jisheng and other writers whose work is banned in China, on Newsnight Wednesday 21 November at 2230 on BBC Two, then afterwards on the BBC iPlayer.