The lords of Carnarvon are best known for the discovery, by the 5th Earl in 1922, of the tomb of Tutankhamun. For the present holder of the title, the challenge lies in preserving a very different historic relic: his own home, Highclere Castle in Hampshire.

Like many a hard-up aristocrat, Lord Carnarvon claims to be struggling to pay the bills on his ancestral home and cannot cover the cost of releading the roof, not to mention repairing one of his lodge houses and clearing the silt from the lake. He says the income from the estate, which comes from the use of the castle as a wedding venue, as well as from a group of farms, a shoot and forestry, leaves him £159,000 a year short of what he needs to maintain the Grade I-listed buildings, the medieval deer park and the Capability Brown gardens.

Lord Carnarvon has received grants in the past from English Heritage and local councils for the repair of the property, whose handsome 1840s gothic-revival facade was the work of Charles Barry, the architect of the Houses of Parliament. But his latest drive to raise funds for the building promises to be a good deal more controversial. He has applied for “enabling development”, under which parts of his 5,000 acres could be turned into a different kind of estate: a housing estate.

Enabling development is a term used in planning circles for projects that would not normally be allowed because they fall in open countryside or other land protected from development, but which are deemed to be acceptable because the money raised from them will be used to restore a historic building or garden (see box, below right).

The Highclere Estate has yet to produce detailed plans, but it has managed to persuade Basingstoke & Deane borough council to draft a policy that would allow for £11.75m worth of development on the estate. The policy is open for public consultation until November 23.

With no plans or architects’ drawings yet on offer, it is not easy to imagine exactly what it would mean – but to raise £11.75m in land sales at current prices would involve some fairly serious development, involving the construction of 50-100 homes. While none of them would be built in the historic 1,550-acre park itself, they would have to be in sensitive locations. Almost all the land owned by the Highclere Estate lies within the North Wessex Downs Area of Outstanding Natural Beauty, which in conservation terms is only one level below a national park.

“We’ve identified 18 small sites around the periphery of the estate,” says Lord Carnarvon. “Some of them are trapped by roads and are of no use for agriculture. It needn’t necessarily mean a lot of houses: in this part of the country, a big house with a lot of land can sell for a lot of money. I do take the point that even if you are building on not very interesting pine woods, there will still be a lot of opposition. But Highclere Castle is unique, and people are keen to see it preserved.”

Lord Carnarvon attempted to sell his plans to local communities at a public meeting held at the castle on October 13, which was attended by more than 100 people. “The atmosphere was attentive,” says Mike Harwood, clerk to the parish council for the village of Highclere. “There is concern about building on land that is designated as an Area of Outstanding Natural Beauty, but my personal view is that anything that is done to safeguard our heritage has to be seriously considered.”

The enabling-development provisions have previously been used to allow the developer Crest Nicholson to build a housing estate around Ingress Park, near Dartford, on the southern bank of the Thames estuary. As part of the deal, the developer had to arrange the restoration of Ingress Abbey, a gothic-style gentleman’s residence dating from 1833, which now stares down to the Thames along a tree-lined boulevard – although most of the original parkland has been lost to new houses and flats.

One project frequently held up as an example of successful enabling development is Stamford Brook, at the National Trust-owned Dunham Massey estate in Altrincham, on the edge of Greater Man-chester. Redrow and Taylor Wimpey are halfway through building 700 homes. The proceeds of the sale of the development land, which comprises 2.5% of the estate’s 3,000 acres, is being ploughed back into maintenance.

Other enabling developments, by contrast, have been successfully opposed. In 2003, the National Trust applied for permission to build 191 upmarket houses and flats on the 15-acre site of the Canadian Red Cross Memorial Hospital, on one flank of the 376-acre Cliveden Estate in Buck-inghamshire. It said it needed £20m to repair the house and grounds, which were given to the Trust by Lord Astor in 1942. Following furious opposition from locals, the application was rejected – although the Trust was allowed to plough ahead with a more modest development of 135 flats for the over55s.

English Heritage, which has responsibility for the preservation of Grade I-listed buildings, says it supports the principle of development at Highclere. “The development would be spread over a dozen possible sites, none of which, as far as I am aware, would have a significant effect on sightlines from the surrounding countryside,” says David Brock, team leader for English Heritage in Berkshire and Hampshire.

If it is successful, Lord Carnarvon’s scheme would be bound to be viewed with interest by owners of historic houses all over England. Where enabling development has been allowed in the past, it has tended to be in cases where there is a derelict building that is an eyesore and in desperate need of being saved. Highclere Castle, by contrast, is in full working order and already generates substantial income.

There are few historic houses in the country whose owners would argue that they could not benefit from cash raised by the building of a house or two in the grounds. But the question is, once you start nibbling at the land around historic homes, where do you stop? Lord Carnarvon says that the £11.75m he hopes to raise will be enough “to secure Highclere Castle for his great-grandchildren”, but can anyone be sure he won’t need to sell off even more land in future? English Heritage took a very different line with Apethorpe Hall, a Grade I-listed ruin in Northamptonshire. In that case, the organisation preferred the government to exercise compulsory purchase powers rather than allow a private developer to restore the building, funded by the construction of 11 new houses on the site of several 1950s homes and a sports hall left over from the building’s days as a school.

English Heritage argued that the new development would spoil the setting of Apethorpe, but taxpayers have ended up footing a very large bill for this purist attitude towards conservation. The building cost £3.2m to buy, and the legal fees to execute the compulsory purchase added up to £400,000. English Heritage has since spent £4m on a new roof.

The hall was placed on the market in May at a price of £4m-£5m, but remains unsold, with taxpayers almost certain to make a hefty loss.

Why could it be permitted?

Under the enabling-development rule, housing schemes – especially in rural areas – that would normally be rejected by the planners can get the go-ahead as long as their proceeds are used to help fund the renovation or restoration of a historic property. Such projects are permitted only provided they do not detract from the “heritage asset” or its setting, and are of the minimum size necessary to raise the money needed.

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