U NLIKE THE tortuous Brexit negotiations, in which crunch time is perpetually postponed, Britain’s energy industry really did mark a decisive moment this week. On October 15th, after a few last-minute glitches, hydraulic fracturing (“fracking”) for shale gas started at two wells on a site in Lancashire. Britain is years behind countries such as America in this (see article). But advocates of fracking argue that the industry could yet transform Britain’s energy prospects, as it has across the Atlantic, if all proceeds as planned.

That is a big “if”. Fracking was last tried in Britain in 2011, by the same company, Cuadrilla. It was rapidly suspended after earth tremors nearby, which the fracking is believed to have caused. Fracking can also pollute the water supply. These and other environmental concerns have made the practice highly controversial. It is banned in some Europeans countries, such as France, Ireland and the Netherlands; the Labour Party has promised to outlaw it in Britain if elected.

A determined gaggle of protesters has set up camp outside the front gates of the Cuadrilla site on Preston New Road. They will continue to pursue cases through the courts to try to shut the operation down. The fact that Cuadrilla’s fracking started within a week of the latest warnings of imminent catastrophe from the UN ’s Intergovernmental Panel on Climate Change has only energised them. They were further buoyed by the release from Preston jail of three of their number on October 17th. The trio had been sentenced for clambering on Cuadrilla lorries last year, but the Court of Appeal ruled that their punishment had been “manifestly excessive”.

With the government’s backing, Cuadrilla will frack on regardless. The British Geological Survey, a publicly funded body, estimates that the main shale gas reserve, the Bowland-Hodder basin, which straddles northern England from coast to coast, could contain about 1,330trn cubic feet (37.7trn cubic metres) of gas, and perhaps more. By comparison, the country consumes only 3trn cubic feet a year, almost half of it from the declining resource of the North Sea. If Britain exploited just 10% of the Bowland-Hodder reserves, it would be self-sufficient in gas for nearly 50 years.

The rewards for Britain’s nascent fracking industry could be equally rich. Francis Egan, the boss of Cuadrilla, estimates that with 20 wells operating, the Preston New Road site could produce £600m ($788m) of revenue. Cuadrilla, which has so far sunk £100m into the project, has a licence to drill in a 1,100 square kilometre area, subject to planning permission. Other companies hope to follow suit: Ineos has permission to drill an exploratory well in Derbyshire, whereas Third Energy and Aurora Energy Resources are hoping to proceed in Yorkshire and Lancashire respectively. It will take thousands of wells to make a fracking industry economically viable. Pipelines will have to be built and a new onshore extraction industry created.

For now, however, much depends on what happens at Preston New Road. Everyone involved stresses that it is an experimental process. The first gas will be extracted early next year, and only by the end of 2019 will it be going into local houses. With an eye on the company’s green critics, Mr Egan promises that it is a “slow and measured” process. If any of the eight sensors at the site detects a tremor with a magnitude of 0.5 or higher on the Richter scale, drilling has to stop. (The 2011 rumble measured 2.3.)

And just in case Cuadrilla slips up, there are plenty of environmentalists just beyond the front gates taking their own round-the-clock measurements and observations of what is going on at the site. Settle in for a long battle.