Mystery surrounds the whereabouts of the heir to a 1,000-acre country estate in Cornwall which was bequeathed to him more than 40 years ago.
John Paget Figg-Hoblyn could be alive or dead say administrators
The Colan Woods Estate near Newquay is making £88,000 a year in rent which is piling up in a bank account.
The Official Solicitor of the High Court has been administering the £5m estate since 1972.
But it said John Paget Figg-Hoblyn, last heard of living in a truck in the US, had stopped corresponding.
"We do not know whether he is alive or dead," said the spokesman.
Mr Figg-Hoblyn, now 81, inherited the estate in 1965 when his father died, but had not agreed to take up his inheritance, the Official Solicitor said.
The estate is falling into disrepair
Next in line to the estate is his cousin John Westropp Figg-Hoblyn, 71, a retired farmer from Missouri.
His wife Geraldine went to Cornwall in 1994 to make a documentary about the estate which tracked down the missing heir and his sister Margaret to a caravan park in California.
And now, fearing that the legacy will be lost, the couple have put out a new call to find the missing heir.
She said: "We know the general vicinity where John Paget Figg-Hoblyn and his sister live, but not the specific address.
"The future of the estate depends directly upon the demise of John Paget, as he is the only inheritor."
Five farms and six houses being rented out bring in a total of £88,000 a year, according to administrators.
The 19th Century Fir Hill manor house, already in ruins when the Official Solicitor was appointed, has fallen further into neglect over the decades.
Russ Walkey, chairman of Colan parish in Cornwall, said: "It is hardly recognisable as what it was.
"I have never heard of anyone being terribly concerned because the deterioration has been going on for so long."