In this episode, we cover the story of a blood-chilling escape from Carstairs State Hospital, which saw two criminals brutally murder three people in a pre-planned getaway.

Four armed police officers made their way south by car from Glasgow wondering what lay in store for them.

What they had been told chilled their blood and made them realise they had only one choice, kill or be killed.

The nature of violent crime in the city has given the four detectives the experience of handling major incidents.

As a result, they had been sent 30 miles to Carstairs in Lanarkshire to assist local colleagues.

That chill November night two patients, Robert Mone, 27, and Thomas McCulloch, 26, broke out of the State Hospital there.

They had murdered two patients and a local police officer in the most brutal of circumstances.

The armed officers knew that they would have little option but to shoot both men if they tried to kill again.

Mone had been convicted of murdering pregnant teacher Nan Hanson, 26, in 1967 with a shotgun in her classroom at St John's RC Secondary School, Dundee.

The former soldier had been expelled from the school in 1964 and harboured a grudge.

He returned three years later and held a classroom of girls hostage. Nanette was shot dead and one of the female pupils was raped.

At his trial, he was declared severely schizophrenic, a danger to the public and sent to Carstairs.

McCulloch was having a sandwich at the Erskine Bridge Hotel in Renfrewshire in 1970, where he complained he hadn't been given enough butter for his roll.

He shot the chef in the face and the manageress in the shoulder and was sent to the same hospital by the High Court.

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The two men formed a close bond and were even said to be lovers.

McCulloch was the brains behind the escape operation. For a long time, he was looked upon as a near-perfect patient.

He showed no violent tendencies, he worked hard in the hospital paint shop and the staff liked him.

It was all a massive deception to dupe the unsuspecting officials.

Over a period of six months, the two men managed to stash away axes, knives, fake identification and uniforms in preparation for their escape.

Early one evening on November 30, 1976, they decided it was time to make their escape.

They pounced first on nursing officer Neil MacLellan, 46, and then patient Ian Simpson, 40.

Paint stripper was thrown in their faces to disable them.

Both men fought for their lives even as they were being hacked to death.

McCulloch repeatedly attacked Neil long after his victim was immobilised while Simpson was stabbed with a pitchfork by Mone.

At one stage, as if he was seeking a trophy of his escapades, McCulloch sliced off Simpson's ears and put them in his pocket.

The duo had also made a rope ladder and within minutes they had scaled the razor-wire high wall that surrounded the hospital.

Once free, Mone lay down on the road pretending to be hurt so they could flag down the first car that passed.

They planned to kill the driver and take the car.

As the driver got out to help, a passing police car stopped and pulled in.

As soon as they stepped from their vehicle, Constables John Gillies and George Taylor were attacked with axes and cleavers.

PC Gillies managed to escape and raise the alarm at a nearby house.

PC Taylor, who was in a very serious condition and bleeding heavily, managed to stop a passing bus, which drove him to the local doctor in Carstairs.

From there, he was rushed to nearby Law Hospital but died a short time later.

At the time of his murder, PC Taylor lived in Carstairs Junction, next to Carstairs village, in a police house attached to the police office.

The local bobby had just begun his shift at 6pm unaware that Mone and McCulloch, had already broken out of the nearby State Hospital about 40 minutes earlier and murdered two men.

The two escapees stole his police van, which they crashed 10 miles away near Biggar.

They tried to murder two men Jack McAlroy, and William Lennon, who stopped to help.

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McCulloch hacked at Jack McAlroy's head with an axe and Mone stabbed William Lennon six times. Somehow, both men survived.

Both escapees drove off in Jack and William's van but abandoned it because they feared they were about to hit a police roadblock.

Mone and McCulloch then walked to a nearby farm, where they threatened a family, before stealing their vehicle and continuing their journey south.

After three hours of bloody carnage, Mone and McCulloch were eventually captured when a police car rammed their vehicle on the A74 north of Carlisle.

Former Detective Superintendent Joe Jackson was one of the four armed officers sent from Glasgow to recapture Mone and McCulloch.

All four were members of the Strathclyde Police Serious Crime Squad then based in Pitt Street in Glasgow.

Both escapees were taken back to Scotland by car, with Mone next to Jackson in the back seat.

In an interview in 2007 Jackson, now retired, said: "Had the situation occurred, we would have opened fire on the two men had they not been recaptured.

"Mone showed no remorse and took great delight in telling us what he had done that evening. He made my blood turn cold."

Also in the police vehicle with Mone was another young detective Graeme Pearson, who went on to become head of the Scottish Crime and Drugs Enforcement Agency.

Jackson added: "In most murders, the culprits show regret. But there was none from Mone.

"He is the classic psychopath.

"On the drive back he boasted how he and McCulloch had made the weapons they used to kill their victims in the workshops at Carstairs, also saying they had forged passports and a stash of gold Krugerrands.

"He was totally happy with what had happened that night apart from the fact he had been caught.

"It was like someone describing a day at work."

Mr Jackson also recalled the trip south to find the killers.

He said: "At one point the chief constable, David McNee, came on the air telling us to be very careful when we caught up with the men as they were known to be in possession of weapons and had 'already proved' (meaning they had already killed three that night).

"There was no way my colleagues and I were going to be additional victims. We had made up our minds about that.

"The police at Carlisle spotted their car and ran it off the road.

"Mone and McCulloch were not seriously hurt and were arrested at the scene and taken to Carlisle Police Office. We arrived minutes afterwards.

"Both were taken to Lanark Police Office where they were charged."

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Mone and McCulloch pled guilty to the three murders at the High Court in Glasgow in March 1977 and were sentenced by judge Lord Dunpark to the first ever "whole life" items handed down in Scotland.

In May 2013, 65-year-old Thomas McCulloch was freed from prison having secured his release through new human rights laws.

McCulloch had used the legislation to have his sentence fixed at 30 years in 2002 - meaning he could apply for parole.

He is now believed to be living in Dundee.

Mone, 73, is still in prison and is one of Scotland's longest-serving inmates. It's not known if he will ever be released.

Last year the family of George Taylor, including widow Sally, 75, launched a campaign for a posthumous bravery medal on the 45th anniversary of his death.

His family believe he is entitled to a variety of honours, including the George Medal, Queen's Commendation for Bravery and Queen's Gallantry Medal.

Their case was taken up by George Barnsley, of the Lanarkshire Police Historical Society and local MSP Graham Simpson.

However, they were told that such awards could not be made after five years had expired.

At the time, the then Chief Constable of Strathclyde Police, Patrick Hamill, had recommended Constable Taylor for a bravery award to the Secretary of State for Scotland, Bruce Millan, but none was forthcoming.

The only recognition of his bravery to date is a plaque inside Hamilton Police Office, which was paid for out of the pockets of local police officers.

The Taylors have however received backing for their campaign from the current chief constable, Iain Livingstone who has decided to give PC Taylor the Chief Constable's Bravery Commendation.

However, his family are hopeful that he will eventually get the national recognition they are seeking.

PC Taylor had four children - David, Stephen, Paul and Michelle. One of his children, Paul, 50, followed in his father's footsteps and joined the police.

He is also remembered on a granite memorial in the gardens of the Scottish Police College at Tulliallan in Fife alongside 290 other officers who have died on duty one the years.

Graeme Pearson recalled his role in the detention of Mone in an interview last year.

After leaving the police he became a Labour MSP for South Scotland and is now retired.

Mr Pearson said: "I couldn't believe that someone who had been involved in the occurrences of that night could sit with me in the back of a police car and be unaffected by the merciless way they murdered these people.

"He seemed calm, he seemed composed and didn't seem at all affected by the events of the earlier evening and he remained that way until we returned to Lanark Police Office."

After bringing Mone back across the border, the then young detective wanted to know his motives.

He realised that both men saw their crimes as a way of getting out of Carstairs and back into a mainstream prison.

That way they could then apply at some future date for parole.

At that time very few people sent to Carstairs were ever released.

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Mr Pearson added: "I was a member of the serious crime squad and we'd been delegated to help local officers in locating the escaped patients and arresting them.

"Before we set off down the A74 we were told we needed firearms and we understood then it was very serious.

"I think he understood what he had done.

"It was his intention to get out of Carstairs as an institution and the events of that night would ensure he'd never go back again."

Mr Pearson continued: "I got the impression that rather than being two people engaged in a single incident their time at Carstairs had made them almost one person.

"McCulloch being the strong able-bodied one and Mone being less impressive physically but mentally really strong and controlling.

"Power was important to them as it is to others who engage in terrible violence as it is more about power than anything else."

In the past, Neil McLellan's widow Marion has spoken about how the murders impacted his family.

In 2009, she recalled the night of the tragedy in one interview.

Marion said: "I was working as nurse at Law Hospital and living in Carnwath, quite close to Carstairs, a mile away.

"I had worked a night shift and I was dozing on the settee in the afternoon and my son John was down in the local club.

"I heard the Carstairs siren go off. It's a distinctive noise and I knew something was amiss, that someone had probably escaped.

"I was a bit worried so I phoned the hospital.

"The guy I spoke to said he was too busy to talk and when I asked about Neil, he said he didn't know anything.

"I remember the detail perfectly, every bit of it. The next person I spoke to about it was my brother-in-law Donald, who lived five doors away.

"He parked his car outside and came in to speak to me. He said, 'Oh, Marion'. I said, 'Don't tell me he is dead'."

Shortly afterwards, Carstairs chief Professor Kenneth MacRae and another senior doctor arrived at the family home to tell her what had happened.

Marion added: "I said I wanted to go to the hospital, and they said it wasn't a good idea but I said I would be going one way or another and nothing would stop me.

"Professor MacRae took me to where Neil was, lying in a corridor. There were no police in sight and no cordon.

"A nurse was standing there. I didn't see Iain Simpson but I found out later that he had been killed too.

"Neil was lying face down and I walked up to him. There was a large section missing from the back of his skull and there was so much blood it was hard to believe.

"I knelt down beside Neil and tried to gather myself and I stayed there for a few minutes.

"Those moments are etched on my mind. How could I ever forget them? "

"It is an image that no wife or husband should have to bear."

Marion continued: "Neil was a very good nurse, he was interested in being good at his job and doing the right thing.

"He didn't regard everyone in Carstairs as psychos or criminals.

"Neil loved children and he has missed out on life with our three wonderful grandchildren.

"We were looking forward to our retirement and we truly would have made the most of our time together."

In the same interview, Marion told how kind-hearted Neil had got to know McCulloch's parents when they visited him in Carstairs.

She said: "They would travel to the jail from Glasgow, via Lanark train station and Neil would give them a lift into Lanark to catch the Glasgow train.

"They wrote to me after the murder to express their sympathy and I actually felt for them because they have been victims too."

In 2007, a chilling insight was given into the mind of Robert Mone.

Details emerged of therapy sessions at Shotts Prison in Lanarkshire designed to help him come to terms with his crimes.

During the classes, he had carefully sketched the layout of the hospital in pencil and then marked the streets in blue biro.

Mone used a ruler to make sure the map was accurate.

The killer remembered the hospital in incredible detail.

He drew in the dance hall, bowling green, woodwork shed and nurses' training centre, and remembered the exact location of the five wards that house the prisoners.

He placed a small pencil cross in the corner of the administration block - to show where he and McCulloch began their killing spree.

As part of his training, therapists have encouraged him to try to understand the impact of his crimes.

In response, Mone compiled a list of all the people his offences have affected.

He counted 26 direct victims of the Dundee classroom siege and the Carstairs escape, then began to work out how many close relatives each of them had.

In a chart called the Ripple Effect, the killer rated his victims and their extended families on how badly he believes his crimes affected them.

As part of his training programme, Mone then wrote: "Twenty-six victims will equate to 520 people directly affected, plus the perpetrator, of course, which brings the figure to 540 people directly affected. "

Criminologist Professor David Wilson, who was brought up near Carstairs, featured the break-out and triple murder on his BBC Crime Files series last year. Then he gave a simple but chilling insight into the minds of both men.

Professor Wilson said: "Neither Mone nor McCulloch had any remorse or empathy.

"They were psychopaths and had underlying personality disorders which meant they didn't recognise the gravity of the crimes they committed."