SEVERAL dozen officials from Beijing are wrapping up their three-year tour of duty in the Tibetan capital, Lhasa. In early July a replacement team will arrive to carry on their work. Among those due to return to Beijing is Zhi Haijie, who is likely to be praised for setting up a new surveillance system in Lhasa.

It was launched in April 2012 in Lhasa’s Chengguan district, where Mr Zhi has been serving as deputy party chief. Officials call it the “grid system of social management”. One of its main aims is to make it easier for officials to monitor potential troublemakers by using intelligence gathered by community workers within areas known as grids (wangge in Mandarin). Chengguan, which includes most of the city proper and some of the rural area around it, has been divided into 175 of them. The grids’ small size (every Lhasa neighbourhood now has several) is intended to facilitate the gathering of detailed, real-time information.

Why bother? Lhasa is already crawling with security personnel and festooned with surveillance cameras. Even before the grid system any Tibetan who raised a protest banner would be leapt on within seconds and taken away (though few such attempts have been reported since security was increased after riots in 2008). But, mostly in the last two years, Tibetan protesters have taken to setting themselves on fire, which has made the authorities even edgier. Only two of about 120 of these acts have occurred in Lhasa but the capital’s religious importance to Tibetans makes any dissent there particularly potent.

These two men, who last year set themselves on fire outside Lhasa’s Jokhang Temple, one of the region’s holiest shrines, were the kind of people the grid system aims to track. Both came from outside the capital and are believed to have been working in a Lhasa restaurant. Such migrants are harder to monitor than registered Lhasa residents. Hundreds of Tibetans from areas outside the Tibet Autonomous Region were expelled from the city in the wake of the two immolations, according to Human Rights Watch, a New York-based lobby group.

Mr Zhi was no newcomer to grid-based surveillance. He had previously served in Beijing as the deputy party chief of a subunit of Dongcheng district, which had pioneered this method in 2004. Last year he told Tibet Daily, an official newspaper, that Dongcheng and Lhasa’s Chengguan district had much in common in their efforts to maintain stability. He did not spell out the similarities, but they are obvious: Dongcheng embraces some of Beijing’s most politically sensitive areas, including Tiananmen Square. Chengguan, said Mr Zhi, would draw on Dongcheng’s “advanced experiences” with grids. In April 2012 Lhasa’s mayor, Doje Cezhug, visited Dongcheng to see how they worked.

Dongcheng claims huge success. Its 589 grids (roughly one for every 1,500 long-term residents—about the same ratio as in Lhasa) are monitored on screens in the offices of Dongcheng’s subdistricts. Information is fed to these by grid staff equipped with smartphones which can upload geo-tagged photographs of anything troublesome, whether a fallen tree or a protester. “Nothing must leave the grid” is Dongcheng’s motto, meaning problems must be nipped in the bud. Both in Dongcheng and Lhasa there are normally six or seven staff per grid. In Dongcheng they include a policeman and a fire monitor. Lhasa’s have an official responsible for religious affairs. The grids also perform such functions as making sure the elderly and sick receive care. But ensuring stability is the priority.

In both cities grid staff are helped by patrols of volunteers wearing red armbands: usually retired people whose role as local snoops long predates the introduction of grids. Human Rights Watch says that in Lhasa these patrols have become more intrusive with the recent immolations, searching homes for pictures of the Dalai Lama and other signs of dissent. Along with the rollout of grids, the Tibetan authorities have been organising households into groups of five or ten. A leader is appointed who becomes a point of contact for grid officials or police wanting information about members of the group. In May Tibet’s party chief Chen Quanguo said these groups should be the “basic unit” of the system, “ensuring…no blind spots”.

In February Yu Zhengsheng, a Politburo member in charge of Tibetan affairs, said the grid system should be expanded to other cities in Tibet to form “a bastion of iron”. Beijing hopes all its districts will adopt the system by the end of the year. In recent years many other cities elsewhere in China have been setting up similar schemes, though human-rights groups say they mostly fail to match Tibet’s security-related fervour. A survey published in December by researchers in Beijing found that Lhasa residents felt the safest of all those interviewed in 38 big Chinese cities.