Our whistle-stop tour of Yorkshire churches has shown us some hugely cherished buildings, full of beautiful things. Towards the end of the afternoon, however, we step inside something very different – a church in spectacular decline.

Somewhere in North Yorkshire – no names, no recriminations – the trustees of the Churches Conservation Trust, the national charity caring for "redundant" churches, are ushered into the pews. Loyd Grossman – chef, TV celebrity and, for the past year, CCT chairman – takes the front pew as parish officials explain their problem.

"This church is literally rotting before our eyes," says one, a campaigner keen to rescue it and perhaps lure the CCT to take it on. Stonework is crumbling, he says, plaster has fallen off the wall in bucketfuls, the bare brickwork is exposed. It looks undeniably grim, in desperate need of help.

What's to be done? Look for funds to preserve it? Convert it to a new use? Another local worshipper has more controversial ideas. "Our core business as a parish is spreading the word of God, not maintaining old buildings," he says, very blunt. "I think the best option is to demolish it."

There are a few raised eyebrows around the pews. Demolition is not a fashionable option in a nation that has suddenly started worrying about its churches. It's estimated that, unless something radical is done, Britain will lose a fifth of its 48,000 churches over the next 20 years. Two are closing down every week and at least £200m a year is needed for repairs. The Government, however, offers only £25m. The Sunday Telegraph, that bastion of British tradition, has launched a "Save Our Churches" campaign and turned to the great, the good and the high-profile for campaigning talk.

As well as the Archbishop of Canterbury and the Archbishop of Westminster, it has contacted such celebrity church-lovers as Joanna Lumley, Griff Rhys Jones and Jools Holland, who went all elegiac about historic churches being "old familiar friends in the landscape that we often take for granted". Holland singled out for praise the work of the Churches Conservation Trust, which has almost 350 buildings in its care. They have been declared redundant thanks to dwindling congregations and crumbling fabric.

The harsh fact (harsh for religious people, at any rate) is that the future of many churches may be as tourist destinations. Some 12 million people a year, after all, visit them for their architecture – 10 times the number who visit them to worship.

The CCT's churches often have the charm of the half-forgotten. Many lurk down winding lanes, over stiles or across fields. Some are always open; many others have a keyholder nearby. For the romantically minded, there's a real excitement in turning a big, heavy key in a church lock, pushing open the creaking door and not knowing what you'll find inside. In its way, it's the ecclesiastical equivalent of Loyd Grossman's TV series Through The Keyhole.

Grossman, whose CV bristles with museum and cultural chairmanships, is leading the CCT's trustees round their annual tour of churches in their care. Every year, they visit a different region; this year it's Yorkshire.

Over three days, the 10 trustees are being bussed between a representative selection of the trust's 31 Yorkshire churches. As well as a lot of fonts and pulpits, it gives them a taste of the county's contrasts, from the post-industrial communities of South Yorkshire (including Edlington, the first church the CCT took on), through the bustling business towns of West Yorkshire to the rolling expanses of North Yorkshire.

It has come as a bit of a surprise to some of the more London-centric trustees. I suppose, says one, that if you live in the South, you expect the North to be all dark, satanic mills. Satanic? This is the Churches Conservation Trust, madam. God is on your side.

Day Two of the tour starts in Halifax, at the toweringly spired All Souls, Haley Hill, where, as Tim Charlson, regional development manager, says, the trust has spent £1m over the past 20 years.

Then on to Leeds, where St John the Evangelist in New Briggate is spectacularly hemmed-in by modern, ever-more-booming, ever-more-apartment-crammed Leeds. Full of dark Jacobean pews, it could easily have become an early victim of changing church fashions. As far back as the 1830s, some regarded it as outmoded and ripe for demolition. As one critic said, it was "all gloom and obstructions without one vestige of its dignity and grace".

The scaffolding is up as the trustees troop in. Rewiring is under way, but there are 40 cups for tea or coffee and two plates of biscuits in front of the monument to William Wilson of Gledhow ("Alderman of this borough"), with its two nuzzling cherubs. The trustees put on hard hats and listen to accounts of the church's past and possible future, with various Leeds council initiatives under way.

Back on the coach, Loyd Grossman systematically checks his messages and texts and phones people ("Hi, Camilla!") to get







them to book restaurants and flights to Boston. We drive on to All Saints, Harewood, nestling in the house's grounds and with an astonishing group of medieval tombs – six knights (mostly 15th century) and their ladies, hands pressed together in perpetual prayer, with little dogs and lions lurking in unexpected places. They encapsulate the Wars of the Roses in a few hundred square feet.

Before a buffet and a further drive on to York (Holy Trinity Goodramgate, the CCT's most-visited church), Loyd Grossman enthuses about the trust's "gold-standard conservation work". Predictably, he talks in a non-churchy way.

"The trust's portfolio of 341 astonishing churches is a very, very exciting bunch of buildings to look after," he says, pointing out how important it is to use redundant churches in new ways rather than "preserve them in aspic like some sort of trophies" (though that can often be part of their charm).

"Some of these churches are very gem-like and very remote, almost like aesthetic objects. Others are big, inner-city churches. And they can all play a huge role in the lives of their communities, in the way that they once did."

That's particularly true in rural communities, where pubs, shops
and post offices, those other local focal points, are closing at such an alarming rate.

"Wherever you look, the parish church is almost always the most beautiful, the most significant and most valued building. Quite often, it symbolises a community. And, on an emotional level, people of all faiths and people without faith are affected by them. They seem to be
what Britain is all about."

He points out that trust churches are still consecrated, are generally full of atmosphere, and that redundancy needn't drain them of life.

And he understands why some less pious CCT enthusiasts enjoy looking at empty churches as pure art and architecture, uncluttered by religion. "Yes, I suppose they're free of a lot of the necessary working clobber that working churches have."

Does the fact that's he's American, where white history is so recent, mean he has a different attitude to these old buildings? "I think either a parish church speaks to you or doesn't speak to you. And age is all relative. If you wander around Egypt, a church like this is brand new."

As for the need to save churches: "The sustainability of parish churches is the single most important architectural issue now. It's about how we help them to support themselves in the future. As Roy Strong has said, the most important heritage issue in the 1960s and 70s was saving the country house. The challenge for the early 21st century is to save the parish church. Old buildings have to adapt to the present circumstances."

And, you might reflect, in the case of the sad, crumbling church somewhere in North Yorkshire, adapting to the present circumstances might mean being knocked down.

Churches Conservation Trust www.visitchurches.org.uk