Roman Polanski engaged in "vulgar and tasteless" flirting with a woman in the days after his wife was murdered, an editor has told London's High Court.
Mr Polanski has denied the incident ever took place
Lewis Lapham, editor of Harper's Magazine, said he was the source at the centre of Mr Polanski's libel case against publisher Conde Nast.
Mr Polanski is suing over claims he made sexual advances to a woman shortly after his wife was murdered in 1969.
Vanity Fair magazine denies libelling Mr Polanski in the July 2002 article.
It said Mr Polanski made advances to a "Swedish beauty" in Elaine's restaurant in New York shortly after the death of Ms Tate.
The magazine now accepts that the incident did not happen when Mr Polanski was on his way back to Hollywood for Ms Tate's funeral but said it occurred about two weeks later.
Ms Tate was murdered by Charles Manson's "family" at the couple's home in Bel Air, California.
Mr Lapham told the jury he was in Elaine's with model Beate Telle when Mr Polanski sat at their table in August 1969.
"She was a very lovely girl. She was a fashion model from one of the Scandinavian countries and a very calm, pleasant, attractive woman",
He added: "He [Polanski] began to talk to her in a forward way.
Sharon Tate was eight and a half months pregnant when she was killed
"He began to praise her beauty and speak to her - romance her.
"At one point he had his hand on her leg and said to her 'I can put you in movies. I can make you the next Sharon Tate'.
"He meant it as a compliment. He was attempting to impress her, wanting to express his admiration for her looks.
"I was impressed by the remark, not only because it was tasteless and vulgar but because it was a cliche."
Mr Polanski's QC, John Kelsey-Fry, said the article implied that after the death of his wife and unborn child, Mr Polanski went "on the pull" and exploited her name as a "tool of seduction".
Retired investment banker Edward Perlberg, 66, then going out with Ms Telle, later told the court he had also been at the restaurant that evening and said she had told him what Polanski had said as they went home in the cab.
Mr Polanski has denied the incident ever happened, saying it "dishonours my memory of Sharon".
Earlier, the magazine's QC, Tom Shields, said it was for the jury to decide what motive Mr Lapham - who was not a Conde Nast employee and came from the US to give evidence under oath - might have had to make up their story.
Mr Lapham appeared in London's High Court on the third day of Mr Polanski's libel case.
Mr Polanski won the right to testify from Paris, where he now lives, amid fears that if he entered the UK he would face extradition to the US, where he is still required to face child sex charges.
The case continues.