John Duffy and David Mulcahy: KILLING TO BE GOD

by Guy Toyn

David Mulchay was the dominant half of the ‘Thriller Killers’ – an evil sadist who felt ‘God-like’ when he killed to demonstrate his power over women.

But he slipped through the net which snared John Duffy, even though detectives were sure he was the accomplice of the diminutive sex monster.

Duffy had been nailed by the size four footprints he left at the scenes of the horrific crimes and the distinctive twine he kept which had been used to bind murder victim Maartje Tamboezer’s thumbs.

Despite six days of questioning and meticulous searches of his home, the Operation Hart team set up to track down the killers failed to find similar evidence to put Mulcahy in the dock with him.

Mulcahy had even arrogantly mocked officers when Duffy was jailed, threatening to sue the force for wrongful arrest.

t was not until a third rapist began stalking Mulcahy and Duffy’s favoured hunting grounds at Hampstead Heath, north London, that an extraordinary coincidence would lead to the solution of a case which had haunted those involved in the original inquiry.

And yet throughout an investigation spanning two decades the answer to the riddle was lying in a dusty British transport police store room at Euston station.

When suspicion began to centre on Duffy, the one realistic candidate as his partner in crime was Mulcahy, who was his only friend.


The rape victims had told of an uncanny, almost psychic understanding between the two men who must have known each other for years.

One said: ‘They didn’t tell eachother anything. It was two bodies but one brain.’


David Mulchay

Another added: ‘The two men seemed to be able to communicate without words – by nodding their heads.’

The pair had been inseperable since they met at in their first days at Haverstock Hill secondary school in North London. Mulcahy would later tell police his friend became ‘almost part of the family.’

As they grew up together Mulcahy began to tower over Duffy physically and mentally, who never exceeded his schoolboy height of 5ft 4 inches and was referred to by Mulcahy as ‘the midget.’

Both youngsters lived near Hampstead Heath and enjoyed ‘spooking’ the courting couples and homosexuals who gathered there.

They developed a love of the martial arts, spurred by the Kung Fu craze of the early 70’s. Together they would relentlessly practice the holds and blows which would later be so effective in trapping their victims.


They also began to share an obsession with the excitement they found in cruelty and crime.

Duffy’s wife Margaret Mustafa told the Old Bailey how he would rape her during bondage sex sessions and terrorise their German Shepherd dog Toby.

Mulcahy would cheerfully tell the jury how he had bound a 12-year-old cousin hand and foot and tossed him into a bathful of ice cubes because the lad had difficulty getting out of bed.

He bellowed with laughter as he snapped photographs of the boy floundering in the melting ice.

In 1976 the pair were convicted of causing actual bodily harm when they shot four victims with an air rifle for fun.

Shortly afterwards Mulcahy suggested they should rape a woman together.

Their ‘wicked bond’ had been cemented by deep feelings of sexual inadequacy – Duffy’s irrational hatred of women sprang from a low sperm count which prevented him from fathering children.

Throughout his life Mulcahy had been troubled by difficulties in maintaining an erection which would drive him to escalating sexual depravity and violence in an attempt to arouse himself.


‘Duffy was the serial rapist. It was his partner who had that aggressive streak and the one who had the desire to dominate and exercise power and control over life and death,’ said prosecutor Mark Dennis.


Ann Lock

‘Mulcahy was getting more out of this. He wanted something more than just rape.  It was the taller man who enjoyed exercising power over their victims, tormenting them, humiliating them on occasions.

‘Mulcahy was an arrogant and cruel character playing with his victims as if the whole thing was a game, getting satisfaction and enjoyment from bullying and picking on the vulnerable.’

According to Duffy, they plotted their first rape because Mulcahy hated the owner of a house in Hendon, north London, and wanted to sexually assault her to ‘teach her a lesson.’

They broke in but the woman failed to come home. Another planned rape at a house in Notting Hill, west London failed to materialise when the woman returned home with a male friend.

In 1981 they escaped with suspended sentences at Alton Magistrates Court when they stole wines and spirits from a store room.  Just over a year later the pair would carry out their first rape attack in a series of crimes which horrified Britain.


The pair armed themselves with a ‘rapist’s kit’ of balaclavas, knives and tape to gag and blindfold their victims.

Soon the Michael Jackson tape ‘Thriller’ would become another essential part of the kit.

‘It seemed to motivate them as they drove, singing along, looking for victims,’ Mr Dennis said. ‘A substantial part of the thrill came from the anticipation of the hunt.’

Several of the rape victims remembered Mulcahy blaming them when he could not maintain his erection in attacks of increasing sadism.

He would stroke the women’s hair tenderly, kiss their neck and ask: ‘Are you a virgin?’ as he removed her clothes.

Running his knife across his victim’s lips he whispering threats to gouge their eyes out or slice off their nipples and revelled in their pure terror.

‘He was no longer satisfied by the sexual aspect, but by power, control, violence and torment,’ Mr Dennis said.

It was the desire for the ultimate thrill, the power over life or death that would cost three women their lives.


A 21-year-old who was walking home from a party in Kilburn in north west London clutching a teddy bear, was to become their first rape victim in October 1982.

Using sticking plaster to stifle her screams, they dragged her into a garden where she was stripped, blindfolded and raped.

The victim recalled: ‘I put my hands up and the taller man said: ‘Don’t worry, it is a knife.’

In March of the following year they targeted a 29-year-old restaurant manager who was walking near Finchley Road railway station.

But the woman bit Mulcahy’s hand and despite being kicked and punched she put up such a struggle they let her go.

An American social worker aged 32 was attacked on Barnes Common almost a year later on January 20, 1984. Mulcahy and Duffy, who were in the area decorating Duffy’s parent’s home, stripped and raped her.

Their fourth victim was a 23-year-old grabbed at West Hampstead railway station and dragged across the tracks on June 3 of that year.

She told the court: ‘They had a knife and said they would cut me if I didn’t do as I was told. All I could say was: ”Please don’t hurt me.”

They laughed as they passed the distraught woman afterwards in their getaway car, joking that they should offer her a lift.


A girl of 22 was gagged with tape after she was seized on Highgate West Hill a month later on July 8.

Fortunately the rapists fled when a neighbour called the police. When the girl was comforted she still had pieces of tape on her wrists, one of which would provide crucial evidence against Mulcahy.

A week later on July 15 two 18-year-old Danish au pairs were attacked on Hampstead Heath as they walked arm in arm laughing together.

One said: ‘He told me to take off all my clothes and lie down. Then he pulled his trousers down to his knees and lay on top of me.’

Three months later the pair were arrested when they were stopped in Mulcahy’s Talbot Horizon with stolen building materials.

A black balaclava was found in the car but the pair escaped with fines after Mulcahy told police he used the mask when he was working as a plasterer on dusty ceilings.

On January 26, 1985 they attacked a 20-year-old German au-pair under a canal bridge at Brent Cross. Her scarf was used as a gag and blindfold as she was bundled towards the nearby bridge.


‘The man without the knife sat down and undressed me. He was not rough but he stripped me naked,’ she said.

Once fluent in English, the woman has refused to ever speak or read the language again or tell her husband of the ordeal.

By January 30 the pair were back trawling Hampstead Heath where they selected a 16-year-old virgin.

Duffy told the court Mulcahy was becoming so violent he broke off the attack fearing his friend would kill the girl.

On February 2 they tried again with a French au-pair who was also grabbed near the Heath but the attack was aborted when she screamed and struggled.

Duffy claimed he stopped another attack on a 23-year-old the following month because he was again worried about Mulcahy’s behaviour when the victim was dragged to a flats near the Heath.

Desperate for another victim, the pair selected a 25-year-old solicitor’s clerk on March 1 and raped her on a bench on the Heath.

By now the sexual excitement on the hunt was not enough for Mulcahy, who was having more and more difficulty becoming aroused.


Four days after Christmas 1985 they targeted Alison Day, who had been due to meet her fiance at his printing firm in Hackney Wick.

The 19-year-old near was snatched at Hackney Wick railway station and dragged to snow covered playing fields nearby.

After both men had raped Alison, she tried to escape and fell or was pushed by Mulcahy into the freezing water of a feeder canal.

Duffy claimed he pulled her out, and Mulcahy was so excited by the incident he raped her again, then tore off a piece of her blouse to throttle her.

He recalled: ‘She was saying things like ”It is only his moustache I have seen, I won’t tell anyone, please don’t hurt me.”

‘I was watching David and the girl. The next thing I noticed was he was putting some material round her neck and starting to twist it.’

Mulcahy later told his accomplice he had killed Alison because she might recognise them. But Duffy said: ‘David actually enjoyed it, saying it gave him power – the decision over life and death.

‘I remember him going on: ”It is God-like – having the decision over life and death.”’


Alison’s sheepskin coat was weighed down with stones and she was hurled back into the water. She was found 17 days later, bound and gagged with her hands tied behind her back.

On April 17, 1986, 15-year-old Dutch schoolgirl Maartje Tamboezer was knocked off her bicycle with a length of fishing line stretched across the path – a technique Duffy had learnt from one of his favourite books, The Anarchist’s Cookbook.


Maartje Tamboezer

The teenager was marched across the fields between Effingham and East Horsley in Surrey and raped by Duffy, who claimed Mulcahy suddenly lost his temper.

‘He was becoming very aggressive – hyper, shouting at the girl,’ Duffy recalled. ‘He then raised his fists and hit the girl.

‘She crumpled to the floor. She was struck on the head, at the side. It was a swinging blow. I noticed he had a rock in his hand, or a stone. She just crumpled up and fell on the floor. I believe she was unconscious.’


Former altar boy Duffy said Mulcahy then ripped off Maartje’s belt and looped it around her throat, telling him: ‘I did the last one, you’ll do this one.

‘He passed me the belt. It had a piece of stick through it which was twisted and he gave it to me in my hand,’ Duffy told the jury.

‘I actually started twisting it while David turned away. I think I just got caught up in it. It is very difficult to explain. I just continued twisting until she was dead.’

Duffy said they both left the scene but Mulcahy returned and set Maartje’s body alight, stuffing burning tissues into her vagina hoping to destroy forensic evidence.

Newly wed TV secretary Anne Lock, 29, still had the suntan from a dream honeymoon scuba diving off the Seychelles when she was ambushed getting off a train at Brookmans Park, Hertfordshire on May 18, 1986.

When the pair spotted her bicycle in the station’s shed they hid in the bushes and waited until she returned.

Duffy said he raped Anne, then Mulcahy threw him the a bunch a keys and he went to collect the car. He told the court: ‘David said he had taken care of it.

‘He was very evasive, like he was playing mind games. He was saying: ”She won’t identify us now”. He was very excitable, buzzing. He was even saying: ”Keep your eyes open for another one.”’


Anne’s decomposed body was found two months after she was murdered in undergrowth just a mile from her home. She had been suffocated with her own sock.

Ten years after the murder of Anne Lock, with Duffy safely behind bars Mulcahy must have believed he would never be caught.cnl_j_duffy.jpg

But on August 6 of 1996 another rapist sprang from the undergrowth in near Hampstead Heath, sparking a chain of events which would lead to Mulcahy joining his friend behind bars.

Ted Biggs, then 34, was a salesman at a bedding shop in Hitchin, Herts, leading the double life of a rapist by night.

He attacked 66-year-old woman on the Heath that summer’s night and struck again in Hampstead in September 1998.

Police launched Operation Loudwater to track down Biggs, who would prey on six victims before he was jailed for life.

By sheer chance one of the officers on Operation Loudwater, DC Caroline Murphy met DC John Haye in a pub. DC Haye had been the exhibits officer in the Duffy inquiry.

They quickly realised the two cases had striking similarities in location, and the knife and the balaclavas that were used.


DC Murphy called Whitehouse prison in Cambridge to make sure Duffy had not been let out on day release and could not be responsible for the offences.

She learned Duffy was in fact being interviewed by psychologist Jenny Cutler, who told her Duffy had given the name of his accomplice as David Mulcahy.

All the surviving exhibits from the original case were re-examined and tested using DNA techniques which were not available in the 1980s.

Samples taken from the clothes of one of the au-pairs Mulcahy raped on Hampstead Heath showed there was only a one in a billion chance he was not the attacker.

Senior officers then found than in an astonishing blunder a piece of tape used to bind the woman attacked on Highgate Hill West had not been tested for fingerprints before it was consigned to the storeroom at Euston station.

Their worst fears were realised when four experts confirmed the fingerprint they found on the tape belonged to David Mulcahy.

Tragically, Mulcahy and Duffy could have been stopped after just three rapes.

Mulcahy was convicted of three murders, seven rapes and five charges of conspiracy to rape after a trial lasting more than five months.

The jury of six men and six women had deliberated for 19 hours and 42 minutes over four days.


Duffy was convicted of two murders, five rapes, and another sexual assault but cleared of Anne’s murder at his trial.

He later confessed to another nine rapes – including that of Anne Lock – six conspiracies to rape and two burglaries with intent to rape.

Described by the judge who sentenced him in 1988 as ‘a predatory animal’ Duffy is now thought to be one of Britain’s most prolific rapists with up to 50 victims.

At the end of Mulcahy’s trial in February 2001 The late Recorder of London Judge Michael Hyam told him: ‘These were acts of desolating wickedness in which you descended to the depths of depravity in carrying the them out.’

Duffy and Mulcahy will never be released.