At that point, Zhou Enlai, China's premier at the time, stepped in. He made it clear that there would be no more "active archeological excavation" on Chinese soil, only "rescue missions".

In practice, it meant that the archeologists would not be allowed to excavate ancient burial sites unless their survival was in danger, either by large construction projects or by being plundered by unwelcome visitors.

The only sites exempt from the ruling were those whose excavation was deemed absolutely essential for studies in the related areas.

Over the past decade, as freediving tomb raiders punched a couple of million holes in the ground in search of graves, the policy has been widely questioned.

The main criticism is that it deprives archeologists of the chance to make their own "preemptive strikes".

No project, no funding

Not only does the policy deny archeologists the chance of uncovering priceless objects and knowledge, but also has profound implications for funding.

"With each excavation project at hand, archeological teams apply for government funding, which they then rely on to pay for their daily operations," said Ni.

"No project equals no funding, and lower incomes for the members of the teams, which explains why they will allow tomb raiders to go in first－to make the site accessible to themselves," he said.

However, despite its shortcomings, few experts believe the policy should be abandoned.

Yue Nan, a writer-historian who has written an account of the excavation of the Dingling Mausoleum, said: "We cannot afford to forget the lessons of the past. That principle should be upheld in the foreseeable future, and not only because we are still at a relative rudimentary stage as far as the conservation of delicate antiques is concerned.

"Forgive me, but archeological excavation shares at least one thing with tomb raiding: Both have removed millions of antiques from their original historical and anthropological contexts, thus rendering them trivial if not completely meaningless."

Wang shares Yue's view. "My sense of accomplishment comes from the integrity of the tombs. Whatever is dug up testifies to the greatness of our ancestors," he said, adding that while protection is paramount, archeological research is crucial to the preservation of memories that would otherwise be totally erased.

"Even a desecrated site speaks to me," he said.

Back in the 1950s, when some of China's leading academicians petitioned for permission to dig the Imperial Mausoleum of Emperor Qing Shi Huang, who unified China for the first time in 221 BC, Premier Zhou told them, "Let's leave something for those who come after us."

Keepers of the flame

Yang Xiaochen belongs to that group. For the past decade, the 29-year-old Beijinger, a member of the "Tombs Association", has regularly spent his weekends wandering around the suburbs of Beijing in search of ancient tombstones.

"A lot of the tombstones I first discovered as a teenager have now disappeared, presumably having been stolen to be sold at antiques markets," said Yang, who these days pays increasingly frequent visits to the sites.

"Sometimes, I return a month later to find the inscribed steles have gone, there's just a vague, wet mark left on the ground," he said.

"This may sound fatalistic, but to me graves are like grandparents; you cross your fingers and hope they'll live forever, all the while knowing that they'll be gone, maybe in the not-toodistant future. But at least I have the photos."