Hitmen driving a distinctive Cadillac-style car and blasting a man in the chest with a shotgun sounds like an over-dramatised screenplay for an American gangster movie.

Add to that the victim's lover being killed eight months later in a bathtub murder made to look like a suicide, and you've got an incredibly hard story to believe.

But 30 years ago, that is exactly what unfolded as east Kent became home to two of the country's most baffling unsolved crimes.

Despite receiving 950 calls from the public thanks to a huge Crimewatch appeal, police have been unable to track down the killers who claimed the lives of Alan Leppard and Brenda Long.

It is thought they were professional hitmen paid to do the dirty work of their employer - yet with no movement in the case for decades, justice looks set to remain unserved.

But police said this week "no case is ever closed" and they take heart from the fact a killer was eventually convicted 20 years after the murder of Debbie Griggs.

The force is therefore continuing to appeal for any further evidence.

Here, we take a look back at everything which is known about the infamous murders that have baffled detectives for decades.

Alan, a 43-year-old quantity surveyor, was gunned down on his doorstep, while 42-year-old Brenda was knocked out with a pad soaked in a toxic chemical and drowned.

Alan Leppard murder

The first half of the tragedy occurred on Easter Bank Holiday Monday 1991 (April 1) when the murderers came for Alan.

The dad-of-one, who had been married multiple times, was living with Brenda - his new partner - in a cottage in Monkton, on the edge of Thanet.

The loved-up couple were planning on soon tying the knot and moved to the village together at the start of the year, living just two doors down from the White Stag pub - a place they frequently visited.

It was at the White Stag where - three weeks prior to the doorstep shooting - a mysterious man wearing a red tie, gold bracelet and gold watch visited to inquire about Alan.

The then-landlord told police he had just opened up for the night at about 6.50pm when the smartly-dressed man walked in and made himself known.

The brazen inquisitor - described as having slick black hair, piercing eyes and aged between 35 and 38 - left the pub after being told the person he sought was not around.

Weeks then past and nothing untoward happened in the village... that was until the Bank Holiday Monday.

Alan and Brenda had decided to go to bed early and were watching TV when they heard a knock on the door at about 10pm.

Looking out of the window, Brenda spied two men standing by a "large white car". She went down to answer the front door, yet the vehicle had left.

Neighbours reported that the American saloon car had been slowly cruising around the village's streets since about 8.30pm, with the occupants seemingly scouting the surroundings.

Less than an hour after the first knock on the door, Alan and Brenda heard another.

The same white vehicle had returned to the Monkton Street cottage, and this time Alan decided to head downstairs and quiz the two strange men.

Opening the door proved to be the 43-year-old's fatal mistake. He was shot at point blank range in the chest with a 12-bore shotgun.

Alan was bleeding heavily but was able to stagger into the living room, before dying in the arms of his lover.

Recalling the tragic last moments, Brenda told Crimewatch in 1991: "He went out the door and then there was an almighty bang and a scream.

"I went to go outside and I went to the corner of the back of the cottage. Alan came around the corner and as he came towards me must have moved his hands as I was completely covered in blood.

"I started screaming. I think he said 'get in!' because he was worried for me.

"He was just a grey colour and he was just going - there was nothing I could do to stop him [from dying]."

Showing up in an American saloon car, having their faces seen by numerous witnesses and using the loudest choice of weapon possible, the killers' methods of murdering Alan come across as incredibly ham-fisted.

Yet somehow, they managed to allude the eyes of the nation and the county's top detectives.

In failing to trace the not-so-subtle strangers or locate the distinctive left-hand drive car, the force came in for criticism in the 90s.

The model of vehicle has never been properly pinned down, but it is thought to have been a Cadillac with fins on the rear.

E-fits showing how the white-haired driver and the well-dressed man in the pub were thought to look were revealed to no avail, while a Crimewatch reconstruction featuring an interview with Brenda failed to bring forward solid leads despite hundreds of tip-offs from the eager-to-help public.

Peculiarly, the Crimewatch episode revealed police believed a separate white-coloured and Cadillac-style car was spotted that same night just over a mile away in Minster.

Two men were seen getting into the vehicle at about 11pm in the car park of the New Inn pub - but they were not thought to be linked to the murder.

Brenda Long murder

The professional hit on Alan would turn out to be the first twist in a tale of two murders, as eight months later Brenda was found dead in the bath of her home in Cromwell Road, Whitstable.

She had moved to the seaside town – where the couple had met while working at P&B Metal Components – in the August following Alan’s murder.

During that time police had no reason to believe Brenda's life was at risk, and she was beginning to go about getting back on her feet.

Yet her new life in Whitstable was about to come to an immediate stop just after Christmas.

On Boxing Day she spent time with former boyfriend Arthur Hibbert, who she had previously been in a relationship with for 12 years.

The car dealer was the last person to see Brenda alive, as on December 28 she was found dead in the bath of her flat.

A suicide note was discovered next to her body and an empty pot of pills was floating in the water.

It was initially thought she had committed suicide but the expertise and keen nose of pathologist Dr Alexander Gibson revealed otherwise.

At the post mortem he noticed a strange chemical smell, which tests would later show was diethal ether – a toxic substance which causes someone to black out when inhaled.

He also found bruising on either side of her nose, in keeping with the theory a pad soaked in ether had been held over her face. If she had taken her own life, the pad would have been found at the scene.

Dr Gibson said: "Someone applied the ether to her face by means of a pad without consent. She had been drinking and it is likely that she lost consciousness very quickly, possibly in just a few seconds, when the ether was administered.

"This was a deliberate and violent assault."

At the inquest, leading coroner Richard Sturt passed a verdict of unlawful killing in what he described as "one of the strangest and most disturbing cases I have dealt with for some time".

Brenda's death was now being investigated alongside Alan's, with the two cases linked.

'She was a very likeable, affable, popular person. She didn't have an evil bone in her body...'

But just like the shooting in Monkton, efforts to track down the murderer - or murderers - came up mightily short and no true motive has ever been established.

Back in 2011, Nick Biddiss, who led the manhunt for the Monkton gunmen, told KentOnline how Brenda was a well-liked person with no links to the crime world.

The former detective superintendent developed a close bond with Brenda as he investigated Alan's murder. He then went to spearhead the investigation into his friend's suspicious death, in what was a "unique situation" for a lead officer to know the victim.

"She was a very likeable, affable, popular person. She didn't have an evil bone in her body," he said.

"There was no reason to suggest they were involved in any criminality whatsoever. They were tragic victims. It's a mystery. We don't know why two men came to Monkton and blasted away her other half.

"Her death was initially thought to be suicide, but after the post mortem it was quite clear it was murder and she had died as a result of a third party."

Police pledge not to give up

Speaking this week, Detective Chief Inspector Neil Kimber, of the Kent and Essex Serious Crime Directorate, says the force still wants anyone who has been holding onto information for the past 30 years to come forward.

He said: "While there is no new update in the case of the 1991 murders of Alan Leppard and Brenda Long, recent cases, such as that of the murder of Debbie Griggs, have shown that justice can still be served in historic cases such as these.

"No case is ever closed and our cold case team carries out periodic reviews into unsolved murders, rapes and other serious offences.

"We continue to appeal for information that may assist us in identifying any new lines of enquiry."

Anyone with information which may help the cold case is urged to call 01843 222289.

To watch the Crimewatch episode with the reconstruction of Alan's murder, click here.

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