Victim Liam O’Brien failed to get a response when he knocked on the door of Beevers’ flat and so he let himself in with a key.
Phil Howes, prosecuting, said that Mr O’Brien walked into a bedroom and the next moment was attacked with a hammer.
Mr Howes said: “He thought the defendant may have mistaken him for a burglar and saw the hammer swinging again. Despite identifying who he was further blows were struck.
“There was then a struggle with the hammer. The victim’s head was bleeding. He was also head-butted.”
Mr O’Brien a number of cuts to his head and has since suffered nightmares and flashbacks as a result of what happened.
Mr Howes told the court that the two men were friends. He added: “They had known each other for 27 years. The defendant lived next door to Mr O’Brien’s parents. They had arranged to meet on this day. When Mr O’Brien did not get an answer he assumed the defendant was out and let himself in with a key he had been given.”
Beevers, 29, of Riseholme Road, Gainsborough, admitted assault occasioning actual bodily harm as a result of the incident on February 22. He was given a 12 month jail sentence suspended for two years with a mental health treatment requirement for two years and a 30 day rehabilitation activity requirement.
Judge Michael Heath, passing sentence, said: “This was a serious and sustained attack. It is clear that this has had a considerable effect on your friend.
“The psychiatrist tells me that for some time you have suffered from a psychotic illness. The problem is that you don’t always take your medication.”
David Eager, in mitigation, said: “This was an attack on a good friend for absolutely no reason save it would seem for psychiatric problems the defendant had.
“He clearly has mental health problems. He has had a tendency to stop taking his medication with these results. He says he will now take his medication. He wants to get well.”