Police later discovered the identity as the body of a serial burglar who was thought to have been trapped during a dark hour burglary operation.
He has been identified as 42-year-old Kevin Gough, a local known to neighbours as an ex convict notorious for burglary.
The remains of the man, believed to be a serial burglar, were discovered by pest control workers in an unused part of the Victorian building at Moody and Wooley Solicitors in Derby.
Staff called a pest control company to get rid of what they thought was a heap of dead pigeons , after noticing an unpleasant smell and infestation of flies in their office.
It is believed the body had been in the chimney for several weeks following an attempted burglary.
It has been revealed that Gough, who had no permanent address, has a string of previous convictions for targeting businesses, and looting their belongings.
In 2010, he was jailed for more than two years at Derby Crown Court after admitting two counts of commercial burglary and asking for another nine to be taken into account.
The firm’s Senior partner Julie Marson described the incident as an ‘awful tragedy’.
She said: ‘We thought it may have been a pigeon so we got a pest control guy to come.
‘That’s when we realised it looked like it might be a human body.
‘That’s when we called the police. A couple of officers came round and they confirmed it was a body.
‘To think that poor chap could have been there for days. It’s an awful thought. We just hope he passed away quickly.
‘You wouldn’t wish this on your worst enemy.’
A spokesman for Derbyshire Police said the death was currently being treated as ‘unexplained’.
He added: ‘Police said forensic investigations were on-going at the scene, and they were keeping an ‘open mind’ about the discovery.
During his 2010 hearing, Gough said he had broken into a sandwich shop and a takeway on the same day a month before he was sentenced, stealing cash and causing hundreds of pounds’ worth of damage.
A number of firms in the historic part of Derby city centre where Moody & Woolley’s office is located have been targeted in recent weeks.
Staff at the firm, Moody and Woolley, were said to be in ‘shock’.
Martina Longworth, a partner at Moody & Woolley, said: ‘It’s very tragic. He must have family and friends around him and our thoughts go out to them.
‘As a firm of solicitors we deal with probate matters, we deal with family matters including child protection so we’re used to difficult matters, and our sympathy goes out to the man and his family and friends.’
Officers were called to the Grade II listed building on St Mary’s Gate in Derby city centre at around noon on Wednesday after the body was found.
Builders were called in to investigate the damage, and found a hole in the roof.
They told workers at the business they thought there may have been an attempted break-in – but the incident was forgotten until the appearance of the unusual smell.