A teenage prisoner plotted the perfect murder from her cell which she attempted to enact within months of her release, the Old Bailey heard today.

Kemi Adeyola’s plan to kill, cut up and dispose of an elderly victim in pursuit of a £3 million fortune was discovered by guards, on 18 neatly handwritten pages.

But she claimed it was part of a novel she was writing and refused to discuss it further, said Sir Allan Green, prosecuting.

Within months, she had murdered former neighbour Anne Mendel, 84, it was alleged.

Mrs Mendel’s husband Leonard, 80, discovered her body covered in coats in the hallway of the house they shared in Elmcroft Crescent, Golders Green, north London.

She had been murdered in the hour it took for him to go to a local travel agent to collect tickets for a trip to Israel they planned to take.

Adeyola, then 17, had lived in the house next door two years before the murder on March 14, last year. Her DNA was discovered in blood on the 4ft 10ins frail pensioner’s body.

Adeyola, now 18, of Camden, north London, denies murder and two charges of perverting justice.

Sir Allan told the jury: "There is written evidence that Kemi had earlier written out on two occasions, plans to murder an elderly woman and steal from that woman’s home."

Adeyola had told police Mrs Mendel had scratched her hand as she helped her cross a road the day before. Sir Allan said Adeyola had lived with her family next door to the Mendels’ terraced house from February 2002 to July 2003.

She told police the Mendels were "quiet but nice people" and had once taken in a young member of her family when she was locked out.

Sir Allan told the court that in October 2004, Adeyola was detained for three months in a Bullwood Hall young offenders institute in Essex.

Her cell was subject to a routine search when letters and other writing was found. He said she had made 18 pages of notes entitled Prison and After: Making Life Again.

Sir Allan said this talked about her achieving her aims to lose four stone from her 11.5-stone weight and make £3 million.

In it she talked of finding a victim to rob and kill. This would involve staking out houses worth millions of pounds in isolated areas.

"She must be wealthy, quite elderly and defenceless," read the document.

An inventory included guns, silencers, bullet-proof vests, drugs, two sharp knives, a motorbike and handcuffs, said Sir Allan.

There would be a period when the victim would be watched. "Visit them disguised as an A-level student from a nearby school," it said.

Then the plan said the victim would be attacked as she arrived home in the dark. "Show the knife to her - then place it against her throat."

The woman would be injected with tranquilliser and then questioned about pin numbers and safe combinations. The woman would then be made to write a letter saying she was leaving her husband for someone else.

She would then be killed, her head and limbs cut off with a butcher’s knife and placed in cling film and black bags before being dumped in bins, said Sir Allan. It ended: "The job must be done by February 2005."

Adeyola had been interviewed by a senior member of staff and a psychologist who were concerned about what she had written.

She allegedly said: "I want them back. It’s a story. The prison staff had no right to take them."

She had walked out of the room when the psychologist asked why she had written about such things. Sir Allan said when police asked about the document after her arrest, she said it was a draft for a crime thriller like the books of American author James Patterson.

Sir Allan said the murder may have been a trial run because Mrs Mendel was not wealthy and did not live in a rural area.

He added: "The plan on paper differed from the plan that was actually executed. It may be the case, and I hope this does not sound callous, that this was an experiment, a dry-run to see how it went."

Leonard Mendel, now 81, told the court he and his wife had lived in the house for 30 years. He said his wife had little jewellery of value. She wore a wedding ring and kept her engagement ring in her bedroom.

He added: "The jewellery she wore occasionally was not of any real value, may be a couple of pounds at most. Some things were of sentimental value which her mother gave her."

The trial was adjourned until tomorrow.

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