Amber Heard Photo: IC

Johnny Depp's ex-wife Amber Heard "stole" her personal assistant's story of being a victim of sexual assault, the former employee told a UK court Wednesday on day seven of the Hollywood star's libel trial.

"Much to my utter shock and dismay, I discovered that Ms Heard had in fact stolen my sexual violence conversation with her and twisted it into her own story to benefit herself," Kate James, who worked for the 34-year-old actress from 2012 to 2015, told London's High Court via video link from Los Angeles. 

"This of course caused me extreme distress and outrage that she would dare to attempt to use the most harrowing experience of my life as her own narrative."

Pirates of the Caribbean star Depp is suing the publisher and executive editor of Britain's tabloid newspaper The Sun over a 2018 story that branded him a "wife beater."

Depp, 57, denies abusing Heard during a two-year marriage that ended in a messy 2017 divorce and several lawsuits.

She claimed he was violent toward her on at least 14 occasions.

James told the court that Heard was prone to drinking and sending insulting messages in the middle of the night.

Ben King, who worked for the Hollywood star for three separate periods between 2014 and 2016, said Heard was often the "antagonizer" in the relationship, adding "the way they argued could make them seem like schoolchildren."

King once had to recover the actor's fingertip, which Depp claims was cut off by Heard with a broken vodka bottle. 

The actress, who is due to testify on Friday, maintains that he sustained the injury while using a telephone. 

Depp's former estate manager Kevin Murphy also accused Heard of asking him to lie to an Australian court during the couple's infamous 2016 run in with the law for flouting quarantine rules by bringing two dogs into the country on his private jet.

"I expressed that I was extremely uncomfortable with doing so, to which Ms Heard responded with words to the effect of: 'Well I want your help on this... I wouldn't want you to have a problem with your job.'"

Heard escaped conviction after eventually pleading guilty to falsifying immigration forms when she brought the dogs into Australia, where Depp was filming Pirates of the Caribbean: Dead Men Tell No Tales.

The court is scheduled to hear from Depp's former partner Vanessa Paradis by videoconference on Thursday. 

In a written testimony already submitted, the French singer and actress, who was in a relationship with Depp for 14 years, called him "a kind, attentive, generous, and non-violent person and father." 

The trial, which is due to last at least until the end of next week, will see US actress Winona Ryder, who was in a relationship with Johnny Depp in the 1990s, also testify in his favor.