A self-styled "sugar daddy" who murdered an escort has failed in his bid to have his sentence reduced.
Multimillionaire Peter Morgan, 55, from Llanellen, Monmouthshire, strangled Georgina Symonds, 25, in January 2016.
His barrister Edward Fitzgerald QC told London's Appeal Court he had been treated too harshly.
But Lady Justice Hallett said Morgan's 25-year minimum term for enacting his "cold-blooded plan" was not "manifestly excessive".
At trial, Morgan told Newport Crown Court he had lost control after learning Ms Symonds was going to leave him, but jurors rejected his defence.
He paid Miss Symonds, from the Allt-yr-yn area of Newport, up to £10,000 a month and described himself as a "sugar daddy".
Morgan admitted killing her after officers traced her mobile phone to his farmhouse near Usk, Monmouthshire.
He claimed he confiscated her phone to stop her buying drugs, but when asked whether he killed her, he told detectives: "Yes. I don't know why I done it."
Morgan, worth an estimated £20m, claimed she threatened to release explicit photos of him to his family if he did not transfer money and sign over a bungalow he was letting her stay in rent-free at Pencoed Castle, Llanmartin.
Using a listening device, he heard her tell another love interest she would leave Morgan after he signed over his bungalow to her.
Despite saying "I done it" to police after arrest, he maintained he was not responsible for his actions due to Aspergers syndrome.
Throwing out his appeal, Lady Justice Hallett said judges accepted "there had been a background of severe provocation and that he had been seriously mistreated and blackmailed."
But, she added: "He put meticulous plans in place so as to escape the consequences of his actions. He didn't waver until it was too late.
"We are not persuaded that the sentence was in any way wrong in principle or manifestly excessive."