Wentworth Woodhouse

“It could have multiple-occupancy, and be part of Sheffield University, with incubation space for start-up businesses, as well as for those that are already established,” he says.

He also recommends that Wentworth copy Stowe, the National Trust property in Buckinghamshire. The building houses a school and the public pay to visit the park.

“Why should only schools like Eton and Harrow have access to these beautiful buildings?” he asks.

However, there is the not-so-small matter of the insurance payout – which is estimated to be around £65 million.

Dame Helen Ghosh, director-general of the National Trust at Clandon

Dame Helen Ghosh, the director-general of the National Trust, and former permanent secretary to the Home Office, claims that the underwriters for Clandon won’t cover an alternative purchase, and that Lord Onslow’s suggestion is “based on a misunderstanding”.

The insurance money cannot be used elsewhere because Clandon is “inalienable” – meaning the property can never be sold or mortgaged – she explains.

But Lord Onslow, an insurance underwriter by profession, believes that an organisation as well-connected as the Trust could come to an agreement with the lender.

The insurance company, Zurich, is sitting on the fence. “We have been flexible in accommodating the needs of the National Trust, as the final decision about the future of Clandon rests on them,” a spokesman comments.

It is the insurance money that will fund the Trust’s partial reconstruction of Clandon. On Monday Dame Helen unveiled detailed plans to painstakingly restore the great Marble Hall, with its double-height ceiling, and the Speakers’ Parlour, to their 18th-century state.

The Marble Hall at Clandon, as it was before the fire “We want to tell the story of the architecture,” she says. The Trust also plans to build a modern exhibition space upstairs, and will run a competition to find the right architect for the high profile and challenging job.

The ruin that was Clandon is the result of an electrical fault in the distribution board. The fire swept through the building with unusual speed and ferocity due to high winds that day, and a disused lift shaft which acted as a wind tunnel fanning the flames.

Even with 16 fire crews put to work, an estimated 90 per cent of the contents was lost, although volunteers were able to save some 400 items most precious items using what the Trust calls the “starred list”. By lucky coincidence this drill had been rehearsed just weeks earlier in a full-scale disaster practise.

Clandon with fire crews still intact

The loss at Clandon can only be estimated on account of the vast amount of rubble that is still inside. In the rooms surrounding the Marble Hall, mountains of wreckage haunt the ashy, broken space.

Describing what happened on that night in April last year, Lord Onslow says: “There were 25 windows on the back wall, each one lit with orange light. The house was alive and now, she’s dead.”

Clandon had been home to the Onslows for 300 years before it was donated to the National Trust by the 5th Earl’s sister Gwendolen, Countess of Iveagh, in 1956, because running costs had become too high. This might go some way to explaining why Lord Onslow doesn’t want the ancestral pile to be restored.

The Speakers’ Parlour at Clandon, as it was before the fire

“Clandon is lost. It’s a ruin now. It decayed instantly. This sad site should be left in peace and tranquillity,” he says. “The last thing we want now is a replica. If the National Trust wants a replica, let them build it somewhere else.”

While Dame Helen described the fire as the opportunity for a new start, the earl views it as a chance for the Trust to reassess its goals.

“This isn’t about me. It is even less about Clandon. It’s about the National Trust and what they are going to do next,” says Lord Onslow. “It is the membership whose voice should be heard. Is this what is best for them?”