The film star Johnny Depp has been accused in court of suffering “blackouts” and having no recollection of his violent past because of his excessive drinking and drug-taking.

During his second day in the witness box at the high court in London, the 57-year-old actor faced allegations that his self-destructive behaviour and jealousy of his ex-wife Amber Heard led him to assault her repeatedly in the course of their four-year relationship.

Depp is suing the Sun’s publisher, News Group Newspapers (NGN), and its executive editor, Dan Wootton, over an article that called him a “wife beater” and referred to “overwhelming evidence” that he had attacked Heard.

The libel case is expected to last three weeks. Heard, 34, has submitted details of 14 occasions during their relationship when she claims she was assaulted by Depp. He denies ever hitting her.

Challenging his account of a flight on a private jet from Boston to Los Angeles in May 2014, when he was alleged to have kicked his wife in the back, Sasha Wass QC, representing the Sun, suggested: “You had a blackout, didn’t you? … You may have done some things you don’t remember.”

Depp admitted in court that he may have blacked out but added: “I do have some memories of the flight ... I’m not a violent person, especially not with women … I deny that I kicked her in the back.”

An email from Depp was read out to the court about the flight, in which he later admitted having stayed up drinking the night before and taking “powders”, a reference to cocaine. Depp’s message referred to himself as having consumed a further two bottles of champagne on the flight, resulting in him turning into an “angry, aggro Injun”.

In another text read out to the court, Depp appeared to apologise to Heard for that behaviour. Wass asked why he had sent it if, as Depp alleged, it had been Heard who had been “badly behaved”. Depp said it had been important to “placate” Heard afterwards.

Wass said Depp had been jealous of the fact his wife was playing the “love interest” in a film opposite the American actor James Franco.

Depp has admitted he was addicted to Roxicodone, a narcotic, pain-relief drug he had been prescribed. He denied being addicted to other substances.

Wass asked Depp: “Do you have a problem remembering some of the things you were doing because of your excessive consumption of alcohol?”

He replied: “For someone who was pretty self-destructive during my life, I have been pretty lucky that my brain is still functioning.”

Earlier the court was taken through an incident said to have been the first time Depp assaulted his former partner. Heard was alleged to have laughed at a tattoo on his arm that had been altered to read “wino for ever”.

Wass said Depp had a tattoo on his arm that used to read “Winona for ever”, engraved during his previous relationship with Winona Ryder. After their relationship ended, the tattoo was changed to “wino for ever”, the court heard.

In 2013, Wass said, Depp had “fallen off the wagon” and was taking drugs and alcohol. “Ms Heard laughed at that tattoo,” she said. “You were in fact acting like a wino and an alcoholic and felt very sensitive.”

Depp agreed: “I was dispirited, after 160 days or so I had broken my sobriety.” He did not recall, he added, Heard making a joke about the tattoo and provoking an argument.

Wass put it to him: “You then slapped Ms Heard across the face and that was the first time it happened.” He slapped her three times in all, Wass alleged, because Heard did not respond but just stared at him.

Depp responded: “It’s not true. It didn’t happen … I didn’t hit her.”

The court was read a series of texts he had exchanged with a friend, the actor Paul Bettany, which, Wass said, reflected his resentment of Heard trying to stop him taking drink and drugs.

In one of them, the court was told, the two men were joking about proving that Heard was a “witch”. In one message, Depp wrote: “Let’s burn Amber.”

Wass suggested the messages, although meant as jokes, were sent because Depp resented Heard acting like the “moral police”.

Depp said he was “resentful of the fact Ms Heard was very aggressive and quite insulting about my use of alcohol”. He also accepted that she “didn’t like me using alcohol and drugs”.

That, Wass said, was at odds with Depp’s previous assertion that Heard had never supported his efforts to give up his addictions.

She then read out an email that Heard had written but never sent to Depp. “I don’t know if I can take this any more,” she wrote. “It’s like there’s a Dr Jekyll and Mr Hyde. Half of you I love madly, the other half scares me. I can’t take him. The problem is I never really know which one I’m dealing with until it’s too late.”

Depp has accused Heard of setting up a “hoax” because her allegations were “patently untrue”.

The court was told that some of the cross-examination would be heard in private, which the media will not be able to report.

The hearing continues.