An alcoholic who told a neighbour he “had seen ghosts” before stabbing him during an ill-fated attempt to go cold-turkey is back on the streets after winning a cut in his prison sentence.

Alcoholic Keith Dundas said he felt “sheer calm” after plunging a seven-inch knife into James Griffith, piercing his bowel, while suffering visions and paranoia brought on by his bid to beat the bottle.

Disturbed Dundas, 53, of Haverstock Road, Gospel Oak, was handed a five-year extended sentence at Blackfriars Crown Court in April 2012 after he pleaded guilty to assault occasioning grievous bodily harm.

He was ordered by Judge David Martineau to spend four years in jail, with an extended year-long licence period to be served in the community.

But three senior judges at London’s Court of Appeal this week upheld an appeal by Dundas over the length of punishment. They quashed the extended sentence and replaced it with two years and eight months in jail

Mr Griffith suffered from multiple perforations to his bowel and internal bleeding.

The appeal judge said he was fortunate to make a good recovery.

It was heard that a week before the attack Dundas began self-detoxing in an attempt to overcome his addiction, which triggered delusions.

After the first visit to his neighbour on the day of the attack, Dundas went to hospital and was given drugs to inhibit his paranoia.

But he became convinced Mr Griffith was posting claims about him on the web.

He bought knives and six cans of high-strength lager, drinking two of them before carrying out the assault.

Dundas admitted the offence after his arrest but denied intending to cause his victim serious harm.

Mr Justice Hickinbottom, sitting with Lord Justice Fulford and Mr Justice Burnett, said: “In all the circumstances, despite all the aggravating features, we consider that a four-year custodial term was excessive and manifestly so.”

Dundas has now served more than half of his new sentence and is therefore eligible for immediate release.