The father of Karen Buckley says he hopes her "truly evil" killer spends the rest of his life in prison.

John Buckley was speaking after 21-year-old Alexander Pacteau was remanded in custody, having pleaded guilty to the Irish nurse's murder.

Glasgow High Court heard that the 24-year-old was killed within minutes of leaving the Sanctuary nightclub on April 12th last.

He will be sentenced on September 8th.

Speaking outside the court, Ms Buckley's father, John, said she was  was randomly targeted by a "cowardly vicious criminal".

Police Scotland Detective Superintendent Jim Kerr believes the sheer weight of evidence led to today's guilty plea.

Ms Buckley had gone on a night out with friends to The Sanctuary nightclub on Glasgow's Dumbarton Road but left alone around 1.00am after telling her friends she was going to the toilet.

Outside she encountered 21-year-old Pacteau, who was drunk. He, too, had been at the club but had left friends inside.

CCTV showed him and Ms Buckley's talking in the street, although detectives say they had not been in contact inside the nightclub.

They believe that Ms Buckley might have got into his car because she was offered a lift home.

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During the journey, CCTV showed the car enter Glasgow's Kelvin Way and picked it up leaving the street 12 minutes later.

It was during that time Karen was murdered. Pacteau grabbed her neck with his hand and hit her over the head up to 13 times with a spanner just over a foot in length. He has not told police what triggered the attack.

The killer then drove to his flat and, upon arrival, wrapped Karen's body in a sheet and hid it in his bedroom while his flatmate and his flatmate's mother, who was visiting, slept in a separate room.

The next morning, Ms Buckley's friends called police when they were unable to contact her. As a full-scale search was launched, Pacteau was conducting internet searches on his phone for chemicals to dispose of a body.

With Ms Buckley's body locked in the bedroom, he went to B&Q on Glasgow's Great Western Road and bought masks, gloves and six litres of caustic soda.

He then went to Poundstretcher and bought more of the chemical. From there he texted his flatmate to check his movements. The flatmate said he would be out until 8.00pm.

Pacteau returned home and, using the caustic soda, tried to dissolve Karen's remains in the bath. His efforts were unsuccessful, so he wrapped her body in a duvet and hid it back in his bedroom, prior to his flatmate's return.

The next day, April 13th, he went to a Tesco store to buy nail brushes and scouring pads and asked a member of staff if they could recommend a product to remove blood from a mattress. He then returned to his flat and put the mattress in the shower in an attempt to remove Ms Buckley's blood.

He then made three separate trips to High Craigton Farm in Milngavie, outside Glasgow, where he had once stored fireworks prior to selling them. This time, he arranged with the farmer to rent two storage units for a week.

On the first two trips, Pacteau burned Ms Buckley's clothing, the duvet he had wrapped her body in and the mattress from his bedroom, as well as cleaning utensils. On the third trip, he took Karen's remains inside the sealed barrel.

The farm at High Craigton in Glasgow, where Ms Buckley's body was found | File photo

Her body was submerged in up to 40 litres of caustic soda, and neighbours recounted to police how they had seen Pacteau struggling to get it from his first floor flat into the boot of his Ford Focus.

After placing the barrel inside one of the storage units, Pacteau had his car cleaned inside and out.

All the time, the search for Karen was intensifying. Police matched an image from CCTV inside the nightclub to the man she was seen talking to in the street. The nightclub manager knew one of the people in Pacteau's company and he in turn identified him.

On the evening of the day he dumped Ms Buckley's body, police went to Pacteau's flat in Glasgow's Dorchester Avenue. On answering the door, Pacteau told them: "I was just coming to see you."

Officers were struck by a strong smell of bleach in the flat and noticed the mattress was too small for the bed frame, as if the original mattress had been replaced. They also spotted rolls of parcel tape and nail brushes which further raised their suspicion. Pacteau also had minor injuries to his hands and arms, consistent with him being in a recent struggle.

Pacteau attempted to lie his way out of the murder.

He told officers Ms Buckley had accompanied him back to his flat where they had consensual sex and that she had left at 4.00am.

Pacteau was asked to attend at a local police station to give a statement as a witness. He was routinely searched and receipts were found for drain unblocker, caustic soda and two padlock keys. One of the keys was subsequently found to open a padlock on one of the storage units at the farm.

Changing story

Pacteau claimed that, during intercourse, Karen had fallen and injured herself. He said he did not realise she had cut herself until the following morning when he saw blood on the bedframe and mattress.

When he realised police were looking for Ms Buckley, he said, he panicked and was scared because he was the last person to be seen with her.

Police released Pacteau while they gathered evidence against him. When they picked him up two days later in a Starbucks coffee shop in Glasgow city centre, he had a reminder note in his pocket of the version of events he had given detectives the first time round.

When questioned again as a suspect for murder, he changed his story, saying Ms Buckley had slipped and hit her head.

He claimed she then started to slap him on the face repeatedly, which caused him to reach to the floor and grab the first thing he could get hold of - a spanner, which he used to hit her on the head.

The spanner was later discovered in the canal close to his flat and Ms Buckley's blood was detected on it.

Despite being valeted, his car still contained traces of Ms Buckley's blood on the passenger side; and his fingerprints were found inside the barrel with the body inside.

The overwhelming evidence against him ultimately led Pacteau to enter a guilty plea at the High Court in Glasgow.

Counsel for Pacteau told the court that he expresses regret and remorse for his actions, which he says were carried out under the influence of alcohol.

John Scullion said he had been instructed to apologise to the Buckley family and Karen's friends on behalf of Pacteau.

Judge Lady Rae called the attack motiveless, senseless and brutal - and said they were the actions of a callous and calculating man.

It is not the first time Pacteau has appeared in court. In July 2014, he was convicted of forging £6,000 (around €8,500) worth of fake £20 notes. He was given a community service order and made to do 225 hours' unpaid work.

He now faces a mandatory life term when he is sentenced for Miss Buckley's murder on 8 September.