To her neighbours and riding friends, Sarah Williams seemed like a "thoroughly nice person" who "oozed confidence" and looked "comfortable in her own skin".

But beneath the veneer of a middle-class ski instructor and dog lover, the 35-year-old had four lovers and had become violently obsessed with one of them, former fireman Ian Johnston.

During her murder trial the court heard how she sent poison pen letters to the wife of one of her older lovers and to Sadie Hartley, Johnson's partner whom he refused to leave.

From her teenage years, Williams had a penchant for older men, meeting her "sugar daddy" David Hardwick when she was just 17 and he 57.

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Despite the huge age gap, Williams was soon sleeping with the heating firm boss, who ended up funding her lifestyle of skiing holidays and horse riding.

He paid £320 ($576) a week into her bank account by standing order as well as covering fuel for her car and even giving her £75,000 ($135k) towards buying a home.

With his help, she soon had a mortgage on the property where she lived and was renting out another as a landlady.

Despite the financial arrangement, Williams went to work when she left school at 18, holding down a number of sales jobs, including at a bank and then at Crystal Ski Holidays at Manchester's Chill Factore indoor ski centre.

It was through skiing that she met the men with whom she would have three affairs in as many years, two of them behind the backs of their partners.

In 2011, Williams met and became "besotted" with married father-of-two Somapat Sitiwatjana, a martial arts expert and skier.

The pair met up for sex in hotels without the knowledge of his wife, Janet, or her partner Hardwick.

Williams told friends she want to "get rid of" Sitiwatjana's wife and even made stabbing gestures to her head whilst making the "Psycho" sound, made famous in the Alfred Hitchcock film.

Sarah Williams, left, and Katrina Walsh, right, have been found guilty of the murder of Sadie Hartley.
Sarah Williams, left, and Katrina Walsh, right, have been found guilty of the murder of Sadie Hartley.

Sitiwatjana feared Williams was getting "too close" and ended the affair after Williams sent him a picture of a baby scan, implying it was hers when it was in fact given to her by a friend.

She also sent his wife a letter in which she called him a "liar, a cheat and a b*****d" and let down his tyres while he was at the indoor ski slopes.

Soon after that, Williams started seeing ski instructor Andy Poole, who she met while staying with Hardwick in a ski chalet.

As with her other flings, Williams and Poole exchanged flirty texts and met up for sex, but their relationship broke down when she refused to leave Hardwick.

Williams then met Ian Johnston, who at that point had been in an on-off relationship with Sadie Hartley for several years.

The pair exchanged numbers and, with both in fairly loose relationships, they started exchanging flirty text messages and were soon meeting up for sex.

Williams would often text her new lover suggestive messages, telling him she was "laying in bed thinking about him".

And she told colleagues she was "hook, line and sinker" for the "alpha male" fireman.

She wrote to a friend: "I want to run away with him... it's too soon to have this conversation like this with him. Being the little psycho that I am, I want to push it along very quickly."

Williams would turn up at Johnston's home in a red high heels and a short skirt and, after getting a key cut, let herself in and waited naked in his bed.

But it seems her strong feelings for Johnston were not reciprocated and less than six months after they first met, he tried to break off their affair, telling her: "I'm in a relationship with Sadie. You knew that before this started."

It was around this point that Williams' obsession with Johnston turned into hatred for successful businesswoman Hartley, whose relationship with the object of her affections continued apace.

In 2013, Hartley and Johnston headed off on a 22-day trip to Ecuador and the following year they moved into a £500,000 house in the Lancashire countryside together.

A furious Williams wrote to old friend Katrina Walsh: "The fireman has feelings for the golden-haired, brilliantly creative and creatively brilliant she-devil... I'm squealing at a pitch that only dogs and bats can hear."

Her anger prompted her to write a poison pen letter to her rival, in which she told of the affair she and Johnston had been having, commenting "the sex is unbelievable" and accusing Hartley of "buying and trapping" Johnston.

Sarah Williams described Ian Johnston as an 'alpha male' and she wanted to run away with him. Photo / Bruce Adams
Sarah Williams described Ian Johnston as an 'alpha male' and she wanted to run away with him. Photo / Bruce Adams

In 2015, Johnston and Hartley went off on a skiing trip together, prompting a jealous Williams to comment to a friend: "Ian and the b**** from hell, how jolly. I really can't stand her."

A fellow ski instructor later said Williams was "infatuated" with Johnston and could become "unhinged" and "psychotic".

Her relationship with Hardwick was also rocky, with a friend recalling she threatened to kill him at a skiing event.

Recalling another clash involving Williams and Hardwick, a different friend said: "Sarah was quite angry... the word that came to mind then and now is 'feral'.

"She was not tamed by the circumstances. We were quite a middle-aged group and it was out of keeping."

After writing of her love for Johnston to long-time friend Walsh, known as 'Kit', Williams began plotting the murderous attack on Hartley.

Prosecutor John McDermott said the pair fancied themselves for years as "Batman and Robin but on the wrong side of the law".

Williams had met Walsh at Collinge Farm in Chester in 2000, when Williams was still a teenager and Walsh was in her late 30s. The women's shared love of horses had blossomed into a close friendship.

But the pair made an odd couple, with a worker at the stables commenting: "Sarah seemed very comfortable in her own skin. I used to look at her and thought she oozed confidence.

"Kit was quieter. She did talk a lot, she just waffled. She was a quieter soul... she was not as confident or as bubbly as Sarah but she spoke her mind.

"I wouldn't say there was a dominant personality. I would describe Kit as a bit in awe of Sarah but it wasn't an obsession."

Heavily-tattooed Walsh, who wore a baseball cap every day to hide her alopecia, made a living by giving horse riding lessons after splitting up with her warehouseman ex-husband Kevin Walsh.

Sarah was quite angry... the word that came to mind then and now is 'feral'.

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She and her ex had enjoyed motor biking jaunts and Kit had supported her husband in his love of re-enacting Viking battles.

Walsh continued to live in the couple's small semi-detached home in the village of Piper's Ash after they split and the trial heard they had a "cordial" relationship as friends.

After initially telling Walsh about her love for Johnston, Williams was soon also bragging about her plans to kill his partner Hartley.

Friends of Walsh believe Williams manipulated her into taking part in the plot, with Walsh's ex saying he could tell Williams was "up to no good".

A neighbour of Walsh said: "I don't know why she's got anything to do with this when it's none of her business. Sounds like it was all this other nutter of a woman."

Walsh's diary first records the pair speaking about murder in September 2014 - 17 months before the killing took place - and the friends repeatedly talked about it in the build-up to the attack.

Walsh's diary shows increased notes about discussing killing Williams's "opponent" with discussion of a "motorbike hit" and even plans to leave an ISIS terrorist flag at the scene to dupe the authorities.

But after the plot was carried out, the trust between Walsh and Williams seems to have disintegrated, with Walsh fearing Williams would now try to kill her too.

From a prison cell before the trial, she told her ex-husband she thought Williams planned to poison her and leave a confession.

Despite sitting just a few feet apart in the dock, the pair barely made eye contact during their trial.

Williams attempted to blame Walsh at trial, claiming her older friend was "excessively" interested in a show Hunted, which features two friends on the run from investigators.

When asked who she thought killed Hartley, Williams said the evidence "points to Kit".