A killer battered his friend over the head with an ashtray before stabbing him 40 times.

Gavin Riley has been ordered to serve at least 17 years in prison for the murder of William Gibb in the victim's home in Ibrox, Glasgow.

Riley, 28, told another man after the murder to get a chainsaw so he could cut up the victim's body but the man instead went to alert the emergency services.

The killer pulled a gun after he was chased by police but was overpowered and detained. It was later discovered to be a BB gun.

He was taken to a police station and was seen to have blood on his clothing, hands and head. As he took off a pair of tracksuit bottoms a large, blood-stained knife with a broken tip was found in the trousers.

Riley told officers they belonged to a relative and added: "I was cutting cheese."

The killer had been friendly with Mr Gibb, 47, who was 5ft 5in and weighed just over seven stones.

Riley had gone out and bought a three-litre bottle of Frosty Jack's cider on the day of the attack and invited an acquaintance Andrew McIntyre "to a pal's upstairs".

They made their way to Mr Gibb's home on Elizabeth Street and spent several hours chatting.

Riley and Mr Gibb ran out of drink and the killer told his victim buy another bottle, which he did.

Shortly after his return Riley dragged the older man from a sofa onto the floor and repeatedly punched him on the face.

He then struck Mr Gibb in the face with an ashtray then hit him over the head with a table.

Mr McIntyre checked on the assault victim and put him in the recovery position after Riley briefly left the flat.

Riley returned again with a kitchen knife with a ten-inch blade before repeatedly stabbing the victim in the back, legs and buttocks. He then knifed him on the left side of his body and slashed his neck.

He tried to wrap the victim in a rug but had difficulty and started cutting his arm with the knife.

Riley told Mr McIntyre to get a chainsaw but he instead went to a nearby close to ask residents to call the police.

When police arrived Riley tried to make a run for it but was chased and caught.

After he was put in the rear of a police van he said: "I don't know what happened. I got pepper sprayed for nothing."

The victim was found to have a gaping neck wound and a stab injury that went into the liver and penetrated the heart. The tip of a knife was found in a stab wound to the leg.

Riley, who had been living at his sister's flat on Elizabeth Street, earlier admitted murdering Mr Gibb on February 1 and 2 this year.

Mr Gibb was found to have sustained at least 40 stab wounds and a similar number of incised wounds along with other injuries.

Defence counsel Gordon Jackson QC said: "It is a bizarre case. There is no proper explanation at all."

He said Riley had consistently maintained he had no memory of it.

A judge told Riley at the High Court in Edinburgh: "Having listened to the account of this dreadful act it is clear you engaged in a prolonged and brutal assault on him."

Lord Boyd of Duncansby said the injuries inflicted on the victim were "truly horrific", adding: "I note you claim to have no recollection of what you did because of the level of your intoxication.

"Clearly, you were under the influence of alcohol and drugs."

The judge pointed out that Riley had been assessed as posing "the maximum risk to the public".