In May 2016, Amber Heard, a 30-year-old actress, arrived at a Los Angeles court seeking a restraining order against her husband, the Hollywood star Johnny Depp.

As she left the building, she found herself surrounded by photographers, journalists and film crews. On her cheek was what appeared to be a mark. The court was also shown photographs of what looked like facial bruising.

She said Depp had "violently" attacked her and in a rage had thrown a mobile phone at her face with "extreme force". There were also allegations of other incidents of domestic violence. She said she had endured "excessive emotional, verbal and physical abuse" and "angry, hostile, humiliating and threatening assaults". Depp denied the abuse.

The restraining order was granted, and soon after the marriage was over.

Four years later the couple were back in court, but this time in London. However, this was not Amber Heard's case - she had not chosen to be here. This was a libel action Depp had brought against a British newspaper, The Sun.

At the heart of the case was his assertion that the allegations of physical abuse were an "elaborate hoax". Depp employed one of the best-known libel barristers in the country to try to prove the claims were untrue.

Over the next three weeks, Heard arrived at court each day and walked past her former husband's fans, who were convinced that it was their hero who was the victim and it was she who had assaulted him. In court her story, photos, memories and the accounts of her friends were all exposed to the world and said by Depp's team and supporters to be part of a plot to falsely prove that he was, as The Sun had claimed in April 2018, a "wife beater".

It was not just the fans and media who were watching carefully. Lawyers were already wondering, if he won, what impact this would have on women coming forward with claims of domestic violence.

Outside, Johnny Depp would arrive each day to cheers. But his behaviour and lifestyle were also under the microscope - and a judge has now ruled that The Sun's allegations were "substantially true".

From court to media circus

"Would you like a Johnny Depp face mask?"

A woman holding a cardboard box offered me a small brown envelope. Inside was a black-and-white bandana and personal note of thanks from Johnny Depp. The woman, who was part of the actor's entourage, disappeared into court as all around me fans and onlookers began to inspect their new scarves.

This was a strange court case.

The rest of Britain was in lockdown, buses and streets in central London were deserted, and yet here, outside the Royal Courts of Justice, there was a crowd, sometimes more than 200 strong. Some wore masks but when Johnny Depp arrived, all attempts at social distancing collapsed in the crush to catch a glimpse.

Inside the High Court, it was even more peculiar.

The Royal Courts of Justice are huge, gothic and deeply solemn. It's a place of stone arches and hushed tones. And in July it was almost empty. I say almost, because there were a few people - a handful of journalists hurrying through security, and also lingering in the hallways and passages a scattering of Depp fans.

One woman showed me her arms, which were covered in tattoos of Johnny Depp. Another man arrived each day dressed as Jack Sparrow, the star's character in Pirates of the Caribbean.

And then at around 10:00 each day they would gather at the door to Court 13. As Depp walked past they would offer messages of support and, towards the end of the case, he was seen giving them all a hug. A little chant of "Johnny, Johnny" could be heard as he walked into court.

Ten minutes later, he was sitting in the witness stand trying to convince a High Court judge he was not a "wife beater".

The 'wife-beating' accusations

The accusations were shocking. Heard said she had been assaulted by him on more than 14 occasions. She said she had, at times, been in fear for her life and left with a broken nose, black eyes and split lip. Vicious, drunken tirades had, she said, lasted for days. There was also a 15th allegation too traumatic and personal to be heard in open court.

It felt like a criminal trial; Depp was being accused of repeated assaults on his former partner, the sort of violence that has sent others to prison. But this wasn't a criminal trial.

It was easy to forget this was a libel battle between Depp and News Group Newspapers, the publishers of The Sun, because no-one from the newspaper was called to the witness stand. Dan Wootton, the journalist whose article had said there was "overwhelming evidence" that the actor was a "wife beater" was not even on the list of 79 names cited in the trial's documents.

And what a list of names it was. The case began with an email exchange about the perils of addiction between Depp and Sir Elton John and then continued with references to a bewildering cast of characters. James Franco, Marilyn Manson, Elon Musk, Winona Ryder, Kate Moss and Vanessa Paradis were all guest stars in a story that took a private world of the Hollywood A-list and blew it apart.

We were shown text messages and video footage of meetings in lifts. The super-rich spend millions protecting their privacy and here was a couple revealing a telephone directory's worth of secrets. No star would do this unless they felt there was something bigger at stake. For Depp, that was restoring his reputation.

Why London?

But why did this battle begin in the UK?

The article with the Dan Wootton byline, in particular the phrase "wife beater" in a headline that was later changed, had given Johnny Depp a chance to test his ex-wife's claims in court - and what's more, an English court.

It would require a much longer article to explain all the differences, but the essence of the legal split between England and America is that if you write something defamatory in London, the burden is on you to prove it is true.

In America, the defamed person has to prove it isn't true, a very different task. It sounds a slender legal nicety but it can make all the difference.

England and Wales's libel law was tightened in 2013, but it is still one of the best places in the world for the rich (and it is a rich person's game) to take on the media. If you want to win a libel case and you have a choice about where to bring it, lawyers will suggest buying a ticket to Heathrow.

And if you want to understand how big an issue this was for Depp's reputation, look at what he was trading. He lived in a world of security guards and private planes. Going to court blew it apart.

If you ever wondered what it was like to be Depp, this case lifted the lid on his privileged but erratic existence, his temper and his history with drink and drugs.

Actress, activist and campaigner

Amber Heard was 22 when she met Johnny Depp on the set of the film The Rum Diary in 2009. He was 23 years older and in a long-term relationship with singer and actress Vanessa Paradis. Heard's wife at the time was the artist Tasya Van Ree.

Two years later, Heard was living with Depp in a penthouse in downtown LA, Depp having separated from Paradis, his partner of 14 years. Heard and Depp married in February 2015, and just over a year later it was over.

Since then, Amber Heard has become a vocal campaigner on the issue of domestic and sexual abuse. The UN Human Rights Campaign named her as a Human Rights Champion for her work promoting women's rights. She became an Ambassador for Women's Rights for the American Civil Liberties Union (ACLU) and she has given speeches and written in the Washington Post and New York Times about her experience of domestic violence.

In the era of Me Too, she was a leading figure, speaking up for women who had suffered in silence by revealing the abuse she had endured at the hands of one of the most powerful people in Hollywood. She was Amber Heard, actor, model, activist and domestic abuse survivor.

When Johnny Depp described her accusations as a hoax, he was not just challenging her story, he was ripping away the foundations of her public profile. There was a lot at stake here.

The entire process, which involved an almost brutal public examination of a couple's private life, has been a warning to anyone who wants to use the courts to restore a reputation.

It was clearly a deeply troubled relationship, but the case depended on proving who had done what to whom.

And in the end, the judge decided it was true to describe Depp as a "wife beater".