Have you actually read the story?
Yes I have.
He wasn't insane. The actual finding was manslaughter due to diminished responsibility - that's diminished responsibility not no responsibility. The diminished responsibility was due to depressive hypochondria, apparently with psychotic symptoms. But the psychiatric report found no evidence that he was legally insane at the time or incapable of having the intention to kill his wife.
The judge appears to have been very unimpressed with him.
"You thought your wife, the victim of this fatal shooting, was not paying enough attention to you and your needs," said the judge.
“She was carrying the entire burden of running that house whilst you took to bed."
The judge noted that Hartshorne-Jones had refused to take his anxiety medication. He lied on his gun licence renewal forms. He had multiple contacts with health professionals on 26 days out of the 42 days before the tragedy. This was not a man who was being ignored. This was a man who failed completely and totally to take responsibility for himself and his mental state so he didn't pose a danger to those around him.
The judge viewed assessing culpability as posing a 'complex challenge'. Hartshorne-Jones made no comment in police interviews. The evidence as to diminished responsibility was accepted by prosecutors and not tried in court. In particular: Judge Levett said that none of the three psychiatrists who had assessed Hartshorne-Jones appeared to have asked him: ‘Why did you shoot your wife?’ According to the psychiatrist, Hartshorne-Jones 'maintains largely that he doesn't know what happened' and 'reserts being asked about' the killing.
This raises questions about the quality of the evidence. It also doesn't really sound like a man overcome with remorse. Instead, he sounds like a thoroughly awful and self-centred man who is still refusing to take responsibility for what he has done.