A retired research and development manager at the old Horlicks factory was found dead at his flat in Slough.
But at an inquest on Monday Berkshire assistant coroner Ian Wade returned an open verdict - acknowledging that it was impossible to know exactly how he died.
Derek Norbury, of Hampshire Avenue, Slough was found on Wednesday, February 21 after the landlord called the police after hearing he had not been seen for days.
A report by PC David Morgan read out at the inquest revealed that he had crowbarred the door to find rubbish strewn everywhere, empty food and beer cans.
Mr Norbury'a body had been so decomposed a post mortem could not identify cause of death, although there were no signs of trauma or violence.
Mr Wade said: "He does not appear to have troubled the local health services at all. The neighbours did not know him.
"Sometimes elderly gentlemen can become more and more introverted."
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