Vile Katrina Walsh was one half of the odd couple who planned the "perfect murder".

Intelligent, artistic and eccentric, but with limited social skills, Walsh, 56, was very different to Sarah Williams, 35, but the pair had shared interests and formed an unhealthily close relationship despite an age difference of 20 years.

Heavily tattooed on her arms, the older woman was in a biker group and rode a Harley Davidson, calling her machine Raven. She also had a horse called Zephyr, used Tarot cards and had a penchant for making jewellery, especially dragon-themed pendants.

Read more: Woman facing life in jail for stun gun murder of Sadie Hartley

She suffered from alopecia, with repeated episodes of hair loss, and was never seen without a hat or bandana.

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As a riding instructor, she first met Williams at stables when her co-accused was aged 12 and while Walsh was on the periphery of the local skiing set. Both were heavily involved in horse riding.

She married Kevin Walsh in 1984, sharing common interests in horses, motorcycling and Viking re-enactment events, but he left her for another woman in 2008.

Walsh, known as Kitt, told friends Williams was supportive during the break-up.

Read more: Woman facing life in jail for stun gun murder of Sadie Hartley

She claimed to have passed O and A-levels with excellent grades and to have gained a Masters after completing a degree.

Witnesses said the older woman was "in awe" of her young companion - and CCTV recovered by police consistently showed Williams striding ahead, with her slightly stooped friend following literally in her wake.

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The women lived in each other's pockets, enjoying foreign holidays together and also spending time watching Harry Potter films on Walsh's bed at her cluttered home in Chester.

Just hours before police swooped after the brutal murder of Ms Hartley, it was suggested the pair had been celebrating executing their plan, both sitting on Walsh's bed as they sang along to a DVD of Abba-themed musical Mamma Mia!.

Walsh accompanied Williams on the trip to Germany to buy the stun gun - taking a detour to look at the final resting place of a Celtic prince.

Read more: Woman facing life in jail for stun gun murder of Sadie Hartley

She bought the car and the tracker to be used on the murder mission, along with the knife - using her Tesco Clubcard - and some of the clothing Williams would wear.

She also looked Sadie Hartley, 60, in the eye a week before her murder, delivering flowers to the unsuspecting victim.

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And in the aftermath Walsh was instrumental in the clean-up and disposal of evidence.

An inveterate diary keeper, detailing the most mundane events of her life, the volumes of documents were seized by police, who discovered Walsh had also chronicled the entire murder plot.

Described even by her own lawyer, Tony Cross QC, as "vile" and "guilty as sin" - he suggested for all her undoubted faults she did not believe Williams would kill and would never have agreed to murder.

Read more: Woman facing life in jail for stun gun murder of Sadie Hartley

Walsh told police she thought she was playing out an elaborate charade with Williams, like in the TV show Hunted.

The defendants ran a "cut throat" defence, both claiming it must have been the other one responsible for the murder of Ms Hartley.

Arrogant Williams made copious notes on a pad, resting on a file balanced on her knee, throughout the trial.

Sat at the opposite end of the dock, Walsh barely lifted her head, the two never even acknowledging each other throughout the seven weeks of the trial.

On arrest, Walsh gave a bizarre, trance-like stream of consciousness commentary telling detectives, "I'll follow the memories" as she led them across farmland to where she had buried the stun gun and other evidence.

As with her claims of a poor memory, it was all an act, the jury was told.

John McDermott, prosecuting, said Walsh had done her best to appear a "zombie" and "the caricature of a fool", but she played "almost gleeful participation in the murder" and in reality was as cold-blooded a killer as her friend.