Earlier this month, the Duke of Sutherland offered two Titians from his personal collection to the nation at the knockdown price of £100m. Art-lovers were - and still are – being urged to dig deep to save the masterpieces for the nation, rather than see them end up hanging on the wall of an oil-rich Arab or Russian.

Now the National Trust is making a similar plea to the public – to save Seaton Delaval Hall, a 290-year-old, Grade-I listed building, set in 490 acres just outside Newcastle. It was designed by Sir John Vanbrugh, the architect behind Castle Howard, in North Yorkshire, and Blenheim Palace, in Oxford-shire. The trust is asking not £100m but a far more modest £6.3m – and it has given itself until the middle of January to raise the money. The organisation has promised a further endowment of £6.9m from its own funds to cover long-term maintenance and running costs.

So, what is special about Seaton Delaval, especially given the trust’s insistence, in recent years, that it is more interested in conserving green space than in saving large historic houses (see panel, below)? “It’s absolutely preeminent architecture, and if it were to come to the trust, it would be in our top 10% of houses,” says David Ronn, the organisation’s regional director for the northeast and Yorkshire. “Many would regard it as one of the most important houses in the northeast of England.” And, he adds, the alternative would be “that it would get sold to a developer and lost for ever” – to the public, at least.

Seaton Delaval was built between 1718 and 1728 for Admiral George Delaval, a naval admiral and diplomat whose career took him across the world.

Delaval saw Castle Howard, completed a few years earlier, and commissioned Vanbrugh to build him his own version – with impressive results.

“It is one of the really exciting examples of architecture of that period,” says Jeremy Musson, author of The Country Houses of Sir John Vanbrugh, which will be published in November (Aurum Press £40). “Seaton Delaval, even though it was finished after his death, is pure Vanbrugh. One of his qualities was being able to realise the dreams of his patrons. The admiral was extremely well travelled, and you feel it is an intelligent building.”

Delaval also died before the hall was completed, and it passed down through a series of heirs, during which time it was lived in only intermittently. In 1822, the interior of the central block was gutted by fire; further damage was prevented by more than 200 villagers who turned out to fight the flames, but the house was deserted for several decades thereafter.

Despite further restoration work – in 1862-3 and again in 1959 – the house remained unoccupied until the 1980s, when Edward Delaval Henry Astley, 22nd Baron Hastings, moved into the west wing, which became his permanent home until his death in April last year. He had spent most of his life working on the hall – restoring the exterior stonework, mending the roof and redesigning the gardens – but the interior of the central block remains unrestored. “It needs to be looked after for the future,” Musson says. “But it isn’t a natural residence.”

The 23rd Baron, who inherited Seaton Delaval from his father, lives much more modestly on the edge of what was once the family estate in Norfolk, where he runs an organic farm and farm shop. With three school-age children, he has no apparent desire to move 250 miles north and live in the property himself.

He approached the National Trust last year, offering it the chance to buy the hall. “I have an enormous tax bill, much of it caused by the house and its contents,” he says. “It seems a huge indulgence and expense to maintain a home I don’t live in, which would have a better use if it was open for the public to enjoy. So I’m crossing my fingers that the money can be raised.” If not, Lord Hastings will consider his options, perhaps holding on to some of the estate while selling the house itself.

Driving down the long, tree-lined avenue that leads to Seaton Delaval Hall, there is no suggestion of what is to come. The industrial town of Blyth, on the Northumberland coast, belches smoke into the sky on the left, with the sea beyond. Suddenly, however, there it is – a miniature Castle Howard, sitting in the middle of the landscape. There is a short gravelled forecourt with a statue in the middle and two long wings that stretch out at either side, cocooning the central block protectively.

Inside, the central, burnt-out shell is like a vast stone marquee. Worn flagstones on the floor and enormous fireplaces recall its former grandeur – as do the graceful long windows, spiral staircases and elegant panelled rooms. Doors at the back of the house lead onto a stone terrace with Ionic columns.

The view is quintessentially English pastoral – a green lawn and meadow with horses grazing, stretching away to a stone obelisk in the distance, in memory of the fatal fall from a horse of a Delaval from a past century. (Another member of the family, who died “as a result of having been kicked in a vital organ by a laundry maid to whom he was paying his addresses”, is not commemorated.)

The sides of the house are not so immediately impressive. The west wing, where the late Lord Hastings lived in comparative modesty (with only six bedrooms), is still closed up. I am told that it is habitable, but was not allowed in there – his son is understandably reluctant, for security reasons, to let anyone see the contents. The stable block opposite retains the original stone stalls, with the names of the horses that once lived there. It is magnificent, but musty, too – there is no heating and it is colder inside the house than out.

It is hard not to be impressed by the splendour of the property, not least because of its incongruous setting, but should the National Trust save it all – and, if so, what should be done with it? After all, once you’ve got sufficiently cold looking round the central block, admired the stables and taken a turn in the gardens, meticulously restored by Lady Hastings, who died in December, there is not a lot to draw the crowds. It is a question being pondered on the chilly day in September when I visit. The group, mainly made up of trust volunteers, are part of the biggest community consultation that the organisation has ever conducted.

“Since we’ve gone public in this campaign [in July], I’ve had more than 150 e-mails – and, out of those, only one person said, ‘Don’t acquire it’,” says Liz Fisher, northeast area manager for the trust, who is coordinating the campaign locally. “At the first public meeting, we had 200 people, and everybody said we should buy it. And at all the public meetings after that.”

A softly spoken Geordie who has lived in the area all her life, Fisher is passionate about saving the hall. “It could be one of only three Vanbrugh buildings that are open to the public – that’s a big thing for the northeast,” she says. “A cultural asset in southeast Northumberland helps to join up the cultural heritage map for the whole of the northeast.”

There are 1m people on the doorstep of the estate, she continues, and the opportunity for culture-led regeneration in the area – which has suffered a significant social and economic down-turn since the closure of the mines in the past 30 years – is huge.

At the meeting, those present discuss a variety of suggestions for what the trust should do with the hall if the campaign succeeds. Ideas for the central block range from putting the floors back in or creating a canvas roof inside to leaving it as it is to show its history. Thanks to its renovated state, the west wing would make for a more traditional National Trust visitor experience, while the stable wing could serve as anything from a tearoom to a writers’ retreat. Proposals on the table include turning the hall into an old people’s home, hiring it out for weddings or creating an arts venue in which to stage concerts.

The next step for the trust will be to draw up a list of potential uses it would be happy with, then, eventually, take proposed activities to the vote. Several local groups are being consulted, and any member of the public who has an interest can get involved. “There’s a lot of history to tell,” Fisher says. “We need to think creatively about how to keep the space alive so the public wants to go in and visit.”

Of the £6.3m the trust estimates it needs to raise, only about half will be spent on purchasing the house – with the remainder covering the initial setup costs. “It’s crazy,” Lord Hastings says. “You look at that house, which is an architectural masterpiece, and you look at a semidetached in London, which would cost more.”

It’s still not much compared with the cost of those Titians, but whether the public thinks Seaton Delaval Hall is worth the money remains to be seen.

To donate towards saving Seaton Delaval Hall, call 0844 800 1895 or visit www.nationaltrust.org.uk/donations

Saving grace: our changing heritage

The National Trust’s highest-profile purchase in recent years was Tyntesfield, a Victorian gothic-revival estate in north Somerset, which was bought in 2002 with the help of a £17m grant from the National Heritage Memorial Fund.

This was something of an exception: Fiona Reynolds, who became director-general in 2001, has shifted the organisation’s priorities away from collections of chocolate-box properties to those that tell a story. “It’s the typical, not the exceptional, that people want now,” she said during celebrations last year to mark the trust’s centenary. “They’d like to know how their own families lived.” As part of this policy, it has bought the Liverpool semi where John Lennon grew up and a row of back-to-back terraced slum houses in Birmingham.

Nor is it only about buildings: the focus is increasingly on conserving green spaces, coastline and landscape. According to the director of communications, Ivo Dawnay, the trust wants to move “from being an organisation sometimes perceived as living behind its own walls to one much more ready to articulate and represent local interests, opinions and viewpoints.”

Hence consultations on the scale of the one for Seaton Delaval: when it comes to saving a building, the public should be as enthusiastic as the trust. “We are for the benefit of the nation, not just elite art connoisseurs or ramblers,” Dawnay says.

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