But now, two years after the building was bought by a developer, the building is being allowed to fall into rack and ruin.

A fortnight ago, on a chance visit to Undershaw, in Hindhead, Surrey, a leading expert on Doyle was shocked to discover its heraldic windows smashed, rainwater cascading through three storeys and the front door left open. Vagrants had left behind beer cans, cigarette packets and their makeshift sleeping arrangements.

After reporting the open door he was reassured by an agent of the house’s owner that the property would be secured. Yet this week, the door remained open and John Gibson — accompanied by a photographer from The Times — was able to walk into the house.

Mr Gibson, a chartered surveyor who is the author of five books on Doyle, told The Times: “What price literary heritage? Here’s the house of the writer of the most well-known character in all fiction and it’s just wide open to the wind, the elements and any vagrant who wants to wander round.”

Undershaw is owned by Desmond Moore, of Fossway Limited — registered in the British Virgin Islands/St Helier, Jersey, according to Land Registry records. Mr Moore, who bought it in 2004 for £1.1 million, said that the house had been “completely neglected” for the past 35 years. “The property is obviously empty. We boarded it up. As with most vacant properties, people pull hoarding off and get inside. Until we can establish a use for the building, it’ s difficult to know what to do with the premises.”

Having had an earlier planning application rejected, Mr Moore has now submitted plans to develop the four-acre property. He wants to split the building into six units and to construct three new detached houses in the grounds.

Mr Gibson said: “The local authority have told us that, if we could find anybody prepared to buy it and run it as a hotel and restaurant, they would use their compulsory purchase powers to buy it and to sell it on to the person prepared to do that.”

Heritage campaigners, including the Victorian Society, are appealing for a benefactor to come forward, as well as trying to have its listing elevated from Grade II to I.

Kathryn Ferry, a senior architectural adviser to the Victorian Society, said of the property: “As a monument of one of our greatest literary figures, it is extremely important.”

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