Kirill Belorusov, 32, strangled Laureline Garcia-Bertaux, 34, and sent fake text messages to her friends and family to cover his tracks as he fled to Estonia.
Ms Garcia-Bertaux was found naked, bound and wrapped in bin bags in a flower bed in her garden in Kew a day after she was reported missing on March 5.
The defendant, who falsely claimed to have cancer, was arrested in the capital Tallinn under a European arrest warrant and brought back to the UK.
The Old Bailey was told how Belorusov had owed his ex-girlfriend thousands of pounds and spun a web of lies to avoid paying her back.
He killed her as he was about be exposed as a “complete fraud” after promising to help Ms Garcia-Bertaux move into a fictitious new home.
A jury at the Old Bailey deliberated for less than two hours to find Belorusov guilty of murder.
Mitigating, Martin Rutherford QC said: “There is a particular feature of this case which has given it a very distinctive flavour. That is the level, extent and breadth of the defendant’s dishonesty.
“The reality is one cannot rely on anything Kirill Belorusov says. He is someone who lies and lies and lies brazenly to this courtroom over and over and over again.
“He is someone who believes in his power to tell lies and his power to be believed.”
Jailing him for life with a minimum term of 24 years, Judge Nicholas Hilliard QC said Belorusov killed his former girlfriend to avoid exposure “as a complete fraud”.
He said Ms Garcia-Bertaux must have discovered his “cruel deception” and he killed her to stop anyone else finding out.
The judge said: “At last she must have seen you as a complete heartless fraud.
“Having seen you giving evidence, I’m sure you held yourself in high regard.
“You could not bear the thought of you being exposed more widely as a total and cruel fraud.
“It was, I’m afraid, all about you. I am satisfied you killed her in an effort to stop being exposed as an imposter and fraud.”
He added: “You are a very calculating person by nature.”
The judge rejected the defendant’s depiction of Ms Garcia-Bertaux, saying she was in reality a “talented, loyal, caring and vivacious” woman who was much loved by her family and friends.
Estonian Belorusov worked in bars and nightclubs, but claimed to have been a movie stuntman and a casino bodyguard for high rollers.
The court heard he met Ms Garcia-Bertaux in 2009, but the couple split up in 2017, after she complained that he was a “slob” and would “needle her about her weight”.
After killing Ms Garcia-Bertaux, the defendant was captured on CCTV buying items including an axe and rubble sacks in Homebase to dispose of her body.
He then sent text messages from Ms Garcia-Bertaux’s phone to her friends saying she was planning a “boob job” or “lypo” and expressing her delight at her new fictitious home.
Belorusov fled to Estonia, while Ms Garcia-Bertaux was reported missing by worried friends after she failed to turn up to work at PR firm Golin, where she was an executive assistant.
She also worked as a producer in the television and film industry and had worked with Dame Joan Collins on the 2018 short film Gerry.
Following the guilty verdict, the victim’s mother Federique Bertaux said in a victim impact statement: “The death of one’s own child goes against nature.
“There is not a moment during the day I don’t think of my Laureline. I can’t touch her, I can’t kiss her any more. I watch videos of her just to hear her voice, hear her laugh, to see how she moves.
“I would give anything to hear her happy moments, sad moments, and to hear her say ‘mum I love you’.
Belorusov nodded to reporters in court and his victim’s tearful family as he was led from the dock to begin his life sentence.