To the wire: the Seaton Delaval Hall appeal

To anyone walking up the drive into the symmetrical embrace of its enfolding wings, Seaton Delaval Hall in Northumberland is as Sir John Vanbrugh designed it in 1718. With a year-end deadline looming fast, the National Trust is still £500,000 short of the £6.3m it needs to stop one of the grandest houses in England being sold on the open market. Photograph: Christopher Simon Sykes/National Trust

On a grey day, Seaton Delaval's funereal air is oddly appropriate. It is regarded as one of the greatest English baroque country houses, arguably the greatest by Vanbrugh, a master of the classical-with-a-twist style revered by many contemporary architects. But by the time it was completed in 1728, both architect and his patron Admiral George Delaval, a younger son who made his fortune at sea, were dead. Photograph: Christopher Simon Sykes/National Trust

When the admiral bought the family estate from a bankrupt younger relative, Vanbrugh recommended flattening the lot and starting again to build a house that – although smaller – would rival the grandeur of his palaces at Blenheim and Castle Howard. Photograph: Christopher Simon Sykes/National Trust

The illusion of stately magnificence vanishes immediately inside the front door. The main block, with the grandest state apartments, was gutted by fire in 1822, and never permanently occupied again. It is being sold by the estate of the last private owners, Lord and Lady Hastings, who lived in what were once the servants' quarters. Photograph: Christopher Simon Sykes/National Trust

The house has an eerie atmosphere, as much magnificent mausoleum as home, with classical statues, busts and imposing fireplaces set into cliffs of bare masonry. However, the empty space would give the trust a remarkably free hand. Photograph: Christopher Simon Sykes/National Trust

A public appeal has already attracted more than £1.5m, including large sums raised by local individuals and groups who want the house and estate to find a new role in a region that has been hard hit by the loss of coal and heavy industry. Photograph: Christopher Simon Sykes/National Trust

No trace remains in the stern interior, with its sweep of cantilevered staircase, of the original rambling family home that had belonged to the Delavals since the Norman Conquest. Photograph: Christopher Simon Sykes/National Trust

For centuries, the house was only intermittently occupied. The magnificent 60-foot stables were only full in the hunting season or when the family filled the house for legendary theatrical parties. In 1953 a county history, compiled as a souvenir for the Queen's coronation year, read: "No longer do its marble halls echo the wild laughter of the gay Delavals." Photograph: Christopher Simon Sykes/National Trust

The garden was remodelled in baroque style in the 20th century. The grounds contain a mausoleum to one of the many Delaval heirs who met an untimely end – according to family legend from a kick from a dairymaid who rejected his advances with fatal firmness. Photograph: Christopher Simon Sykes/National Trust