But David Harris, 68, was tripped up when one of the "hitmen" turned out to be an undercover police officer.
Harris was naked in bed with Ugne Cekaviciute, 28, when he was arrested by police.
He had met her while she was working in a brothel, and he became infatuated with her.
He offered two men £200,000 (US$260,000) to kill Ms. Allinson, but they reported it to the police, who set a trap for him.
Harris was covertly filmed as he approached the undercover police officer and tried to do the deal.
But when he came to trial at the Old Bailey, Harris, who had worked on various TV shows, including police drama The Bill, said he was researching a novel, called Too Close to Kill.
Harris was unable to produce a single word of the novel.
The jury found him guilty of soliciting murder, and he was sentenced on Friday, July 14, after the judge ordered mental health reports.
The court heard Ms. Allinson still believed Harris' "fabricated fantasy" and does not accept he planned to kill her.
His lawyer, Anthony Rimmer, told Friday's hearing Ms. Cekaviciute was now "out of the picture" and Harris' relationship with Ms. Allinson was an "open question."
Sentencing him, Judge Ann Molyneux QC, told Harris:
"For your pipe dream, for your obsessive infatuation with a young woman, Ms. Allinson, who had protected and nurtured you, was to die a painful and terrifying death in an isolated spot."
How it all unravelled for the "calculating, manipulative" man that required the expertise of our Major Crime Team. pic.twitter.com/9tHLfYpHY9— CityofLondon Police (@CityPolice) 14 July 2017
"Her death was to fund your life. You had used her until she had outlasted her usefulness to you. All that you wanted from her was that she should die and you should inherit her money," Judge Ann Molyneux QC said.
The court heard Ms. Allinson, a retired scriptwriter, had lost her sex drive after suffering from breast cancer, and Harris began an affair with Ms. Cekaviciute.
Harris lied to his partner about umpiring cricket matches and visiting his brother in hospital when he was actually having sex with Ms. Cekaviciute.
The court heard Harris had a "narcissistic personality disorder" with manipulative traits and showed no remorse.