IN GENERAL, governments are loth to attack anything that routinely appears in children's books (this newspaper once dubbed that the Richard Scarry rule, after a popular illustrator). From farming to firefighting, some things resonate so strongly with the public that only the boldest politicians will risk a scrap. It thus shows either remarkable courage or folly that David Cameron's government is deep into its second public fight of 2011 with the National Trust, a huge charity whose holdings read like a bedtime-story index, including 40 castles, hundreds of woods, beaches, mansions, farms and a dozen lighthouses.

With some 50m visitors each year, the National Trust is as integral to many British childhoods as Marmite or picnics in the rain. It has heft in the adult world, too. With almost 4m members in England, Wales and Northern Ireland (Scotland has its own, sister organisation), the trust has more than seven times as many paid-up supporters as all Britain's political parties put together. Trust bosses cite that statistic in their rows with the government, the latest of which is over a bid to loosen planning laws to establish a presumption in favour of “sustainable development”.

The trust has long spoken out against airport expansions or other schemes that menace its properties. But it was a slumbering giant in national politics: a genteel guardian of crumbling aristocratic piles, through which deferential heritage fans were herded behind velvet ropes. In the past decade, however, the trust has undergone a cultural revolution, adapting to a country from which deference had vanished as surely as liveried footmen or dressing for dinner.

Today, members are encouraged to feel almost like collective owners of its properties, lounging on lawns, playing ancient pianos or enjoying games of croquet. Stern guides have been replaced by volunteers offering fancy-dress outfits or cooking lessons to children. Slogans such as “time well spent” and advertising showing families roaming the countryside play expertly on the anxieties and aspirations of parents in a crowded, time-stressed island.

Still more recently, that evolution has been accompanied by a public political awakening (this year, for the first time, the trust is lobbying politicians at all three political-party conferences). Strikingly, it is Mr Cameron, who wants to cultivate a “Big Society” built around volunteering, charity work and local communities—ie, rather like the National Trust—who has borne the brunt of this new assertiveness.

In the fight over planning, the trust has played rough. It has placed petitions in its stately homes (over 100,000 people have signed), and sent concerned letters to all its members. Its website offers protest posters and the chance to e-mail MPs.

Ministers are determined to avoid the fate they suffered in February, when a bungled privatisation of state-owned woodlands was scrapped after the National Trust (among others) decried it. Dame Fiona Reynolds, the outfit's director-general, says she did not seek either confrontation. But she points to the charity's founding statute, which gives it a formal role promoting the preservation of lands and buildings of beauty or historic interest, and acknowledges it wields considerable clout in public debates.

The row over planning laws is not over. Ministers insist they are “resolute” in their determination to push through a new framework that at once hands powers to local communities to shape new building projects, but at the same time makes it harder for villages or towns in many rural areas to say they want no development at all. One minister accused campaigners, including the National Trust, of “nihilistic selfishness”, arguing that a chronic shortage of new homes only hurts future generations. Yet there are signs that the coalition is feeling the heat. The prime minister recently wrote to Dame Fiona calling Britain's landscapes a “national treasure” and urging dialogue.

His conciliatory tone looks wise. It is not just the trust's 60,000 volunteers, or its localist commitment to serving home-grown produce in its tea rooms, that makes it seem a more sensible model than an adversary. In the complex, frenetic place that is 21st-century Britain, the National Trust has created a parallel world of wholesome, family-friendly calm, rooted in an enviably self-confident approach to history. Mr Cameron would love to achieve half as much.