A 34-year-old escort conned her "sugar daddy" out of £2.5 million after he fell in love with her, a court heard.
Henry Sless, a retired Deloitte's executive, found escort girl Louise Caplan online and they started dating, despite their 31-year age gap.
The court heard Caplan asked the millionaire to be her "sugar daddy" in exchange for £150,000-a-year, but Mr Sless managed to negotiate the fee down to £10,000 a month.
Both Caplan and Mr Sless lived in upmarket Buckinghamshire, the woman in the village of Chalfont St. Giles and Mr Sless in the town of Marlow, the court heard.
Prosecutors told the judge that Caplan bought herself a £1 million house with Mr Sless' money which she obtained by lying that she was investing in businesses in Dubai and Dublin. She also bought artwork worth £300,000.
Mr Sless, who was 65 years old at the time, showered Caplan with gifts worth more than £1 million.
He also parted with another £2.5 million which he wrongly believed the wannabe businesswoman was investing, Aylesbury Crown Court heard.
Jon Swaine, defence counsel for Caplan, said: "It was a sad situation of two people who had fantasies. Each had their own fantasy. Hers was that she wanted to be a successful businesswoman and his came at a time when he was unhappy in his personal life.
"He made decisions that were disastrous and astonishing for a man with his expertise and background. The decisions he made were not made using his head, that is for sure."
Judge Francis Sheridan heard the couple met via the online escort website Adult Works in November 2017 after Mr Sless agreed to pay her £400 for sex.
Prosecutor Stefan Weidmann said: "Mr Sless said in a statement 'it felt like we clicked immediately and within a few days of our first meeting Ms Caplan sent a message saying she would have married me if I would have been 10 years younger and she was 10 years older.
"We met five or so times in the first year and we were in contact on a daily basis. I instantly fell for her."
As the relationship developed, Caplan began to demand money from Mr Sless, the court heard.
In a statement, Mr Sless said: "Sometime in late November or early December 2017, Ms Caplan came to me and asked me if I would be her 'sugar daddy'.
"She asked me to give her £150,000 a year, I negotiated it down to £10,000 per month."
Judge Francis Sheridan heard how the wealthy tax executive showered Caplan with gifts worth £1 million over the course of their relationship.
It was also revealed that the couple had met on at least six occasions for sex, although the judge suggested it could have been more times.
However, the court heard that the escort defrauded him out of at least £2.5 million.
Caplan spent more than £1 million on a luxury house in Farnham Common, as well as nearly £313,000 on artwork and £619,000 on luxury retail goods, despite having previously had an annual income of only £7,000, the court heard.
The judge was told that despite the loans Mr Sless was handing out, the veteran accountant did not demand any paperwork.
Prosecutor Stefan Weidmann said: "When asked why he would give such enormous loans on an informal basis Mr Sless said he the pair to be in a long term relationship and he believed that they had a future together and they would be married and together raise Ms Caplan's daughter."
However, Judge Sheridan questioned: "Of course he would have had paperwork, he was an accountant? What am I missing?"
Mr Weidmann admitted that Mr Sless was a man of "staggering naivety", despite his vast experience.
He had believed that the money was going to be spent on property development in Dublin and Dubai, despite having seen only very limited evidence of their existence.
Earlier, the hearing had been delayed by nearly three hours after Caplan had to be examined under the mental health act.
During the hearing, the escort was often tearful and was visibly emotional at the mention of her daughter.
Defending her, Mr Swaine revealed that she had attempted to use the money genuinely to pursue her dream of becoming a successful interior designer, and it was only when the bills began to catch up with her that she turned to fraud.
He said: "She intended to use this money in a business but she was hopelessly out of her depth. She hired expensive accountants who advised her that she had no hope of success.
"Her huge error was not to go to Mr Sless and say I have been stupid and I have let you down. She had no hope of paying this all back."
Caplan had earlier admitted one count of fraud.
She arrived at Aylesbury Crown Court to hear her fate carrying a Louis Vuitton designer bag containing personal possessions to take into prison.
Sentencing her to five and a quarter years in prison, Judge Sheridan said: "I am in no position to tell the truth of how many times he took advantage of your sexual services.
"It was at least six times but I am strongly suspicious about that given the extremely large figures in this fraud. This had all the hallmarks of a business arrangement and if it was business, it was certainly not done properly."
As she was led away, Caplan remained standing in the dock, before she waved to her mother, who sat in the public gallery, and told her to pass on her love to her daughter.
