Whilst the council has 'prevaricated' for year after year, both the pensioner who originally applied to exercise her 'right to buy' and her daughter have died, London's appeal court heard.
Although declaring Mr Calvert's case 'hopeless' in law, top judge, lord justice Ward, said that did not mean he had not suffered a grave 'injustice' and urged the council to make him an offer.
Mr Calvert earlier said of the council: 'They have driven my family one by one into the grave. That is no exaggeration. There must be a way through this unfairness; it is all grossly unfair.'
And Lord Justice Ward told the appeal court: 'What troubles me is that, if your story is right, there have been years of prevarication by the council in dealing with this application for the right to buy.
'It's a pretty horrific state of affairs ... if half of what you say is true, the London Borough of Southwark has behaved disgracefully.'
After urging the council to do a deal with Mr Calvert, the judge, sitting with lord justice Waller, told him: 'What we have made is a subtle degree of judicial intervention - otherwise known as putting the boot in'.
The council agreed to issue a formal explanation of the delay in processing the family's right to buy application within the next 21 days, a document the judge said he would be 'interested to see'.
A copy of today's judgement will also be sent to the council housing department 'so that they might reflect upon it.'
Southwark LBC also promised the court they would consider whether it would now be legally possible and right to make Mr Calvert a tenant or give him an opportunity to buy the property.
Mr Calvert's mother Arsha and father Gerald became tenants at Thomson House in 1969. When he died in 1981, she took over the tenancy and, in 1984, made her first application to exercise her right to buy.
She again applied in 1991, but died of cancer in 1994 before her application was dealt with.
Lord justice Waller said a dispute arose over whether Mrs Calvert's daughter, Beatrice, who had cared for her mother in the final years of her life, had a right to take over the tenancy.
Five years passed before Beatrice's right to 'succeed' her mother as tenant was upheld by a court and the judge observed: 'That matter too seems to have taken an excessive time to resolve.'
Beatrice made her own application to buy the property in 1999, but died the same year, aged 53 - again before the matter was dealt with by the council.
Lord justice Waller said that, by law, only two members of a family could succeed to a tenancy and, due to the death of his mother and sister, Mr Calvert was left with no rights.
The council was granted a possession order over theproperty in September last year and all Mr Calvert's challenges to that decision have since been dismissed.
Lord Justice Waller refused Mr Calvert permission to appeal further, saying the law was clear and the Appeal Court had 'no jurisdiction' to deal with the matter.
But he told the court: 'Mr Calvert appears to have a substantial basis for complaint about the delays which occurred whilst his mother and sister were alive. That naturally gives us very serious cause for anxiety.'
He added: 'That does appear, on the face of it, to produce a moral obligation on the council to consider whether what appears on its face to be an injustice can be remedied.'
The judge said it might turn out that it was 'just bad luck' that Mr Calvert's mother and sister died before their right to buy applications could be dealt with.
But Mr Calvert, currently living in north-west London, did appear to have a 'moral claim' against the council, he added.
Dismissing Mr Calvert's appeal, lord justice Ward told him: 'We can't correct every injustice in the land unfortunately.
'But we have done more than perhaps we should in trying to come to your help.'
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