Picture: Police Scotland

Ian Macdonald, 55, launched the horrific assault on Eric Martin in broad daylight as he was walking on Gylemuir Road, Corstorphine.

He told the pensioner “I am very sorry about this” and then added “I shouldn’t have done that” while Mr Martin lay injured.

The High Court in Edinburgh heard that Macdonald was “very calm” after repeatedly stabbing Mr Martin in the neck and chest with a kitchen knife. The judge was told that Macdonald did not suffer from any mental disorder and offered no explanation for the attack.

Sign up to our daily newsletter The i newsletter cut through the noise Sign up Thanks for signing up! Sorry, there seem to be some issues. Please try again later. Submitting...

Great-grandfather Mr Martin, who is now 87, spent nearly a fortnight in hospital with life-threatening injuries, and needed 15 stitches on his face and neck to save his left ear.

Macdonald admitted attempting to murder Mr Martin on December 1 when he appeared in court yesterday.

Advocate depute Lisa Gillespie said that Mr Martin, a retired engraver who had been in the army in the mid-1940s, was in good health and fit and active before the attack.

He was used to walking twice a week to the Tesco Extra in Corstorphine to buy groceries, and was walking home from the store when the attack happened.

Macdonald stopped the attack when a builder got out of his van to tend to Mr Martin. He reportedly said “I’ve stabbed him” then added: “I’ll need to phone the police. I shouldn’t have done that.”

The man told Macdonald he would call the police and told him to stay where he was, which he did, while the man and another passerby tried to help the victim.

Macdonald was seen by a doctor at a police station to assess his mental state.

“The accused gave an account of waking that morning as usual, taking a knife from the kitchen drawer and leaving the house with the intention of visiting a local park. On leaving his house he had seen the victim, whom he did not know, and had stabbed him. He offered no explanation for his conduct,” said the advocate depute.

Concerned by his behaviour and passive description of events, the doctor called in a consultant psychiatrist.

But unemployed Macdonald, who lived alone in Gylemuir Road, gave a similar account to the psychiatrist, who found no signs of mental illness.

Mr Martin did not want to complete a victim impact statement for the court case as he found it too upsetting to think about the incident.

He has, however, made a good recovery and remains in good health despite the traumatic attack.

Defence solicitor advocate Brian Gilfedder said: “It is a very unusual and perplexing case.”

Judge Lady Wise ordered background reports and remanded Macdonald in custody until his appearance next month for sentencing.