Benjamin Field, who killed an older man after making him change his will, and betrayed another retiree, worked in Northamptonshire while he was doing his crimes.
The murderer from Olney, just over the border with Northamptonshire, worked part-time in a Towcester company from 2015 until his capture last year.
A former director of business told that Chronicle & Echo He always met Field when he visited the premises and even a Christmas party, but he never thought he could handle his shocking crime.
"I used to be in the room a lot and he was sitting there and I just thought he was quiet talking only to people who were good for him – one of those guys," he said.
"He probably looked at me and thought I could not get anything out of him and thought I was irrelevant."
His curriculum vitae, which was used in court, states that from 2015 onwards, he worked in administration for one to two days a week.
The current business owner, whom we do not want to name, said that the agreement with Field was "ad hoc at best" and came about when he was living with her neighbor.
"Mr. Field occasionally picked parcels into the store, that was the scope of his activities," she said.
"While the whole affair was depressing for all concerned, we have nothing more to add."
Field was unanimously convicted on Friday (August 9) at the Oxford Crown Court of murdering Peter Farquhar of Maids Moreton, Buckinghamshire.
The 28-year-old from Wellingborough Road, Olney, has led the 69-year-old author into a relationship, manipulating him with drugs and mental torture, and suggesting to his friends that he was demeaning and killing him in October 2015 and trying for it like one Accident look like.
Field had already pleaded guilty to four fraud cases, some of which were related to Mr. Farquhar's neighbor, Anne Moore-Martin, whom he also had a relationship with and deceived her with thousands of pounds in 2016 for his brother's phony kidney disease ,
Thames Valley police chief investigator described Field as arrogant and incapable of human empathy. Had he not been stopped, he would have presented a continuing threat to society.
All this happened while working in Towcester, and the former director was astonished when the whole case was published in the local and national news.
"His entire life seemed to revolve around the way you deceive people, he had books on them and computer searches on them, it's all bizarre," he said.
"I think he thought he was smarter than anyone else and could have turned everyone upside down and could do whatever he wanted, thinking it was all a game and living in a fantasy world."