Lin Russell was walking her two young daughters – Megan and Josie – back from school, strolling through fields of swaying corn and warm sunshine in a picturesque part of the Kent countryside.

With their dog Lucy in tow, the sisters had just arrived back at Goodnestone Primary School after attending a swimming gala in nearby Canterbury.

They were heading back to their home in nearby Nonington. But fate was to intervene in the most evil of ways.

Confronted by a man as they walked along Cherry Garden Lane, within minutes, academic Lin, 45, and Megan, six, had been brutally battered to death with a hammer after being tied to a tree in a sun-dappled copse. Josie, nine, had been left for dead. All had been tied up with strips of the towels they had used for swimming. Even Lucy was not spared.

The crime occurred 27 years ago – July 9, 1996 – in Chillenden, a pretty hamlet lying midway between Canterbury and Dover. Enough time for the dust to settle – for the stain it left on the community and the wider country to fade. Yet all these years later it continues to generate headlines.

And at the heart of all of them is a simple question – did the man convicted of the crime actually do it?

Gillingham’s Michael Stone – a man with a violent past, mental health issues and a history of drug misuse – has spent 26 of those intervening years behind bars. He continues, to this day, to insist he is innocent. His refusal to acknowledge any guilt has seen him miss the chance to apply for parole. An increasing number agree with him.

And it is the long-held anxiety over the strength of evidence which convicted him which has prompted the latest TV documentary on the case.

The Russell Murders: Who Killed Lin and Megan? is a well-crafted three-part series showing on Sky Documentaries – an in-depth look at the case and once again poses the question...did Stone actually do it? But does it shed any new light on the case all these years later? Does it provide anything other than conjecture on the case?

The answer is ‘probably not’ but it does do a very fine job in highlighting the key elements of such a grisly crime.

There is a reflection on the impact it had on the local community at the time – the fear and the intrusion into their lives by the arrival of a press pack. The national media descended in their droves, taking up residence, in the days which followed the discovery of the bodies, in the nearby Griffin’s Head pub.

The impact on the people involved in those first moments is both harrowing and clearly emotional all these years later.

Richard Leivers – the Kent Police officer who saw the dead bodies and carried Josie Russell from the copse when he noticed she was still alive – speaks of the profound impact it still has on him all these years later. “Nothing,” he reflects, “could prepare me for what I saw.”

They are, so often, the forgotten people in events of such horror.

The role of the media comes under scrutiny too – both in its coverage at the time and its subsequent relationship with key figures in the ensuing murder case as well as its portrayal of Stone after the guilty verdict (“truths were distorted” says one expert). Yet much of the narrative is told by those reporters who were on the ground at the time.

But once the details are established, it is unease in the police case – which would form the basis of Stone’s conviction – which dominate the storytelling in this documentary. It is, for the most part, a well-trodden path.

Stone, himself, features heavily – heard in telephone conversations with his long-time barrister, Mark McDonald, with whom he speaks “every day”.

“It was about seven in the morning,” says Stone, speaking from HMP Frankland in Durham, as he recalls the moment in July 1997 when he was arrested close to his home in Gillingham. He was 37 at the time.

“I went out to get some milk. I was walking back when about five police cars pulled up around me. They said ‘don’t try and run Mick you won’t get far’. They pointed out all the police to me – everybody was police, even the lollipop lady and the builders’.”

His sister, Barbara Stone – who has long campaigned for his release – added: “When he was being questioned he answered all their questions which was unusual for him as he’d normally give ‘no comment’ answers. He said to me it was a very serious crime and he wanted them to eliminate him, quickly.”

That trip to his local shop in Gillingham was the last time he tasted freedom.

But ultimately, the programme drills down to a closer examination of the case against Stone. It is, clearly, far from convinced.

For those unfamiliar with the crime, it is a remarkable one. Despite the brutal savagery of the attack, there was no forensic evidence linking Stone to the crime. In fact, the only DNA recovered was so weak it would be difficult to match it to any one person. Josie, who miraculously survived, did not pick Stone out at an identity parade.

As Jim Fraser, head of forensic investigations at Kent Police at the time, says: “Could he have done it? Yes. Did he do it? That’s a completely different question.”

Stone was proven to be in Medway four hours before the crime took place (he signed a timed receipt in a branch of Cash Convertors) and he did not closely resemble the photofit circulated by Kent Police, as described by a witness who saw a man exit the lane the murders took place in a car.

His original trial – held at Maidstone Crown Court in 1998 – hung on the evidence of three men. All had been prisoners in neighbouring cells to Stone while he was on remand. They all claimed he had confessed the crime to them. All the details they revealed had, however, been printed in the newspapers.

One would later be revealed as having received payment from The Sun newspaper and a promise of more following Stone’s conviction; another admitted making the whole thing up the day after Stone’s original trial. It would result in the conviction being quashed and a re-trial ordered.

Stone says leading up his first trial, he was so fed up with people claiming he had admitted to the murders, that by the time he was moved to Canterbury Prison he’d asked to be put in an isolated cell.

Yet it was there his cell neighbour, Damien Daley – held on charges of arson and robbery – claimed to have heard Stone admit to the crimes again. His testimony, would, eventually, see Stone jailed. Twice.

“You can have a strong argument,” says Stone, now 63, “or you can persuade through emotion. They shell-shocked [the jury] with that for three weeks.”

Daly – whose own charges were “mysteriously” dropped after assisting with the case – is currently serving a life sentence for his role in the – unrelated - murder of a drug dealer in Folkestone in 2014.

However, the programme features an interview with an anonymous former cellmate of Daley’s – apparently filmed in Folkestone – who claims Daley admitted lying in the Stone case. “He looked me in the eye,” says the former con, “and said it was all lies. You can’t get any clearer.”

The judge at Maidstone Crown Court instructed the jury that if they did not believe Daley’s testimony, Stone should be acquitted.

“When the jury came in,” recalls Stone, “I just looked at them and I knew straight away.”

As his defence barrister during the case, KC William Clegg, tells the documentary: “I felt the verdict was against the weight of the evidence.”

It remains hard to argue against that.

The re-trial was conducted in Nottingham in 2001. However, Stone’s reputation had spread nationwide by then following the massive coverage following his first conviction.

The evidence was fundamentally the same – Daley again providing the one key piece of non-circumstantial evidence linking Stone to the killings. Again, Stone was convicted.

Claims Daley had lied, however, saw the case, in 2005, referred back to the Court of Appeal – and one Stone’s legal team felt confident would finally prove successful.

Heard before a panel of three judges, the verdicts were upheld.

A famous picture of Stone leaving that hearing – head shaved and wearing distinctive yellow and green prison overalls – was captured as he was led back to the security van he was travelling in.

“When I came out of the appeals court the media were there,” says Stone, “and they shouted out ‘Michael’. I shouted out, right at the top of my voice ‘I’m an innocent man’ to reach the media. And if you look at my face [in still photographs] it looks like I’m going psychopathic or something – but I’m actually shouting ‘I’m an innocent man’.

“It hurts me because that photo makes it look like I’m ranting.”

But despite repeated efforts to overturn his conviction, it is only in the last few years any real opportunity for any case to be presented to the Criminal Cases Review Commission (CCRC) has emerged.

In 2017, Stone’s legal team – who admit in the documentary that at this stage they had reached a “dead end” – received a letter from a prisoner who said Levi Bellfield had confessed to the Russell murders.

Serial killer and rapist Bellfield – whose victims included Surrey schoolgirl Milly Dowler and who had a track record of attacking women with a hammer – apparently admitted to the killings, explained how he had done it and that he was the man seen by the witness.

There is no denying the original photofit issued by police bears a resemblance to Bellfield.

Stone’s legal team travelled up to Durham – Bellfield is in the same jail as Stone – to get more information.

Explains Stone’s barrister, Mark McDonald: “From that meeting, we got a lot more detail. We had the description by Bellfield, of what they were wearing, how he did it, who he hit first, how he murdered them, who he tied up, how he’d killed the dog. He said he knew the area very well.

“If you want to go back to the Court of Appeal, you have to convince the CCRC. So I drafted a full commission to the CCRC, putting what Bellfield had said together.

“Bellfield wanted to get it off his chest, but Bellfield said we couldn’t tell anyone. That it was just between ‘you, me and CCRC’. Within hours it was leaked to The Sun newspaper.

As a result of it being leaked, Bellfield goes up the wall. He writes to Kent Police saying ‘it’s all a load of lies – I’m withdrawing it’

“As a result of it being leaked, Bellfield goes up the wall. He writes to Kent Police saying ‘it’s all a load of lies – I’m withdrawing it’.”

But then, earlier this year, Bellfield produces another signed confession – this time witnessed by his solicitor – admitting he carried out the crime.

Bellfield, however, has a track record of lying to the authorities – of fake confessions.

In his latest confession he apparently says: “I was there. I did carry out this crime”

But the evidence remains elusive – the CCRC unmoved. Stone’s legal team insist they want exhibits from the murder scene re-examined, forensically. They believe it could result in DNA being identified which could prove the killer.

As his barrister concludes, it comes down to which of three men – all found guilty of murder – do you believe: Stone, Bellfield or Daley?

Kent Police’s only contribution – other than historic clips and comments from former employees – is merely a submitted statement at the end of the programme insisting that Stone has been tried and found guilty on two occasions.

Notably absent are Josie and her father Dr Shaun Russell – only featured in historic media interviews. You cannot help but feel the pair of them – both subject to such horrific trauma in their lives – would rather the rest of the world forgets the crime which shattered their lives and robbed them of their loved ones. Both have long since left Kent – returning to the peace of North Wales where they had lived before the tragedy.

Stone, however, will clearly not rest until his name is cleared.

He concludes: “Josie and Shaun Russell blame me for that crime. It really tears me apart thinking they think I did that. That’s the worst part of it. I want them to know I didn’t do that.”

Which, of course, begs the so far unanswered question...just who did?

The Russell Murders: Who Killed Lin and Megan? is on Sky Documentaries and available to stream on Now TV.