Glasgow Crime Stories: The married policeman who murdered his lover while out on beat duties

In the late evening gloom and drizzle, he spotted a crumpled body lying on the roadside.

At first, John thought that it was a drunk or some poor unfortunate who'd been attacked and left for dead.

However, as he got closer he realises it was the body of a middle-aged woman. From his cab, he radioed for the emergency services.

When the police arrived a few minutes later it looked as though the mystery woman had been the fatal victim of a hit and run.

But one of the traffic cops called to the accident PC William Kevan wasn't so sure.

In a simple hit and run, there would have been one set of tyre marks at either side of the body. Whereas here there were several.

There was only one explanation - the victim was already on the ground when the car ran over her.

Worse than that the car had run her over several times

Her head and facial injuries were also the type seen following a violent attack than a car accident.

She had been brutally murdered and run over to make it look like a road accident.

The City of Glasgow Police launched a press appeal for anyone who might recognise the woman, as she had no identification on her at the time.

It didn't take long for local woman Mrs Johnston to get in touch.

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Her friend, Catherine McCluskey, had asked her to look after her young baby for the night.

Catherine was 42, a single parent with two children, both by different fathers.

Something that was frowned on at that time in post-war Britain.

Mrs Johnstone became worried when her friend did not come home that night to pick up the baby, little realising that she was lying dead in a gutter.

It was while she was being interviewed by the police that the friend dropped another bombshell.

Catherine had been in a relationship with a serving police officer and they both planned to make a new life together.

Therefore the first person detectives had to track down, if only to rule out, was the victims mystery policeman lover.

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Mrs Johnston had never met the man and only knew his surname - Robertson.

Catherine had also told her friends that he was the father of her second child.

There were a number of Robertsons in the City of Glasgow Police and the investigation team were facing a long slog until they got a phone call from a sergeant at Orkney Street Police Station, Govan.

He suggested they start with 33-year-old married father of two Constable James Robertson.

Big Robbie as he was nicknamed was known to have been seeing another woman and had problems in his marriage.

Constable Robertson when questioned denied knowing Catherine McCluskey.

However detectives quickly established that Robertson had been patrolling close to her Gorbals home around the same time she was murdered.

It soon became clear that the beat cop was living a double life.

His beat partner PC Dugald Moffat confessed he had been covering for Robertson for some time to allow him to slip off for couple of hours, when things were quiet, to see his mystery woman.

That's exactly what had happened on the night of the murder.

Robertson had gone off to see his mistress around 11pm and turned up again for duty two hours later.

The period covering the death of Catherine McCluskey.

It transpired the cop had met Catherine while working the Gorbals beat and they became lovers - but he hadn't told her he was married.

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He also owned an Austin car which had been stolen and had false number plates.

A quick forensic search of the car revealed Catherine's blood and fragments of her flesh, hair and clothes.

Constable Robertson was arrested for murder and remanded in Barlinnie Prison in Glasgow to await trial.

The charge stated that he struck Catherine McCluskey on the head with his rubber truncheon and deliberately drove over her body.

Robertson also faced additional charges of housebreaking and theft.

While being interviewed he admitted knowing Catherine McCluskey but not to having an affair or killing her.

He also admitted he had sneaked off shift to see her that night in his car.

She got out of the car in Prospecthill Road where the argument continued.

Robertson said he had stormed off, jumping in the same car and driving away at speed.

Feeling bad about the row. he had changed his mind, braked hard and reversed back to where Catherine was. He felt a bump. Getting out of the car, he saw he had driven over her body.

Robertson claimed he then drove off in a panic and rejoined his beat partner for the rest of his shift.

That was PC Robertson's defence when he stood trial at the High Court in Glasgow on November 6, 1950, before Lord Keith and a jury of eight men and seven women.

The involvement of a city cop in an unmarried mother’s violent death was a media sensation of its day.

A terrible and brutal murder had been committed and the police were accusing one of their own.

Such was the public interest that a huge queue gathered outside the court every morning, hours before proceedings began. Scores more had to be turned away every day.

One key witness was the victim’s sister Elizabeth McCluskey who said she had no idea who had fathered the children of her unmarried sibling.

She had asked her sister the intentions of the youngest child’s father.

Elizabeth said: “She told me that he could not do anything as he was a married man and she had found out too late.”

Robertson denied in court murdering Catherine, claiming that he didn't really know her that well.

On the night of her death he had picked her up outside her home in Nicholson Street near his beat in Cumberland Street.

They drove around the Southside, during which time she asked him for money for her rent and they argued.

Robertson repeated his claim that they both got out of the car in Prospecthill Road where he accidentally knocked her down and ran over her body.

None of this explanation fitted with the forensic evidence which showed that Catherine had been assaulted first and rendered unconscious.

In reality Robertson had decided to end the relationship with Catherine as he was paying her money each week on top of the money he gave to his wife for the upkeep of their home and to provide for his own children.

It's not known why the argument had turned to violence or why Robertson ever thought he would get away with the crime.

One theory is that he concocted the lie of not really knowing Catherine to protect the reputation of his own family.

And in the absence of DNA evidence in those days it could not be proved that he was the father of Catherine's second child.

The fact that he had drove back to his beat and resumed his patrol as if nothing had happened did not sit well with the jury.

Robertson who had taken an oath to protect and serve had been proven to be a thief, a liar and a man of dubious morals.

After a trial lasting seven days, the jury took just 64 minutes to find the PC guilty of murder on November 13, 1950.

He betrayed little emotion as sentence was passed and he was led down to the cells.

An appeal against conviction failed as did a petition for a reprieve of the death sentence.

Almost five weeks later at 8am on December 16, the infamous executioner Albert Pierrepoint made legal history when he hanged James Robertson.

The PC, who was a member of the ultra strict Plymouth Brethren, was the only serving policeman in Britain executed for a crime committed while on duty.

The case features on the Glasgow Police Museum website, which recognises that even law enforcers have to accept one of their own can do wrong.

Their article warns:"Any member of the force who succumbs to temptation during the course of his duty is subject to the same relentless investigation as any other law-breaker.

"Constable James Ronald Robertson was such a man and from the moment he became suspect, no effort was spared to prove his guilt."