I have returned to New Delhi to find that a motley collection of gangsters known as “the sand mafia” and the name Durga Shakti Nagpal are on everyone’s lips in the monsoon-soaked Indian capital. Let me explain why a bunch of crooks and a 28-year-old woman named after the Hindu goddess of power have so enlivened Delhi’s dinner conversations.

It is common to complain about corruption in India, and no surprise that it comes 94th out of 176 – equal to Benin, Greece and Mongolia – in Transparency International’s Corruption Perceptions Index, which tries to quantify the rottenness of a nation’s public sector.

But it is only occasionally that a scandal erupts to illustrate how the corruption actually works, providing the granular detail, so to speak. Ms Nagpal is an officer of the elite Indian Administrative Service, who was working in Noida near Delhi as a subdivisional magistrate in the state of Uttar Pradesh. She was suspended in July, ostensibly for having endangered communal harmony by supervising the removal of an illegally built mosque wall.

Her real misdemeanour – according to almost everyone other than the notoriously corrupt UP government– was to have tried to halt the illegal mining of sand for construction. Sand extraction to supply India’s building sites is no small matter. Tens of thousands of cases of illegal mining are reported every year, and the practice can change the course of rivers and threaten cities, including Noida, with flooding and landslips.

A committee hurriedly sent by the central government’s Ministry of Environment and Forests to investigate the problem in Ms Nagpal’s district found “rampant unscientific and illegal mining” along the Yamuna river, the Ganges tributary that runs through greater Delhi. The Samajwadi party and the politicians that run UP– a state with a population larger than that of Brazil – insist that Ms Nagpal was suspended because of the mosque, not the sand mining.

Civil servants have expressed outrage at the way she was suspended and charged with wrongdoing by politicians. Narinder Bhati, the Samajwadi leader, boasted at a rally that he had secured her suspension “within 41 minutes” of speaking to Akhilesh Yadav, UP chief minister, and his father Mulayam Singh Yadav. It was also suspicious that Ms Nagpal’s colleague, the district mining officer who had spearheaded the campaign against the sand miners, was transferred two days earlier.

Not every IAS officer in the land is a martyr to probity and the rule of law. Some are inevitably suborned by the politicians. But the brave ones risk their comforts and sometimes their lives to do their jobs. In April I interviewed Sunil Kendrekar, the district collector (officer) of drought-stricken Beed in the state of Maharashtra, who had just survived an attempt to oust him at the behest of powerful landowners and local politicians because he opposed corruption and illegal water pumping.

Ashok Khemka – an IAS officer transferred by Haryana state last year after challenging the legality of a lucrative land deal by Robert Vadra, the son-in-law of Sonia Gandhi, leader of India’s governing Congress party – has this week returned to prominence with the leaking of his 100-page report on the case. Mr Khemka wants an examination into all such deals to “expose the diabolical game of looting public wealth”, although the Haryana planning department says nothing wrong was done.

Only rarely, however, do IAS officers become as prominent as Mr Khemka or Ms Nagpal. The normal practice with awkward bureaucrats immune to threats or bribes is to transfer them to obscure jobs or to investigate them for supposed malpractice. The IAS is one of the institutions that is supposed to underpin the rule of law in the world’s largest democracy, but like the banks of the Yamuna it is constantly being undermined by corrupt politicians and their business allies who trade illegally in the country’s most valuable commodities.

One result of the public furore over Ms Nagpal and the sand mafia is that the price of building sand in Noida has tripled over the past fortnight as illegal supplies (that is, almost all supplies) have dwindled. The shortages will not last, and the sand mafia’s diggers, trucks and tractors will soon be at work again along the Yamuna despite the best efforts of Ms Nagpal. The rule of law in India is too weak and the commercial pressures too strong for it to be otherwise.

victor.mallet@ft.com