A British father and daughter who survived a bombing at an Ariana Grande concert have won their harassment lawsuit against a conspiracy theorist.

Martin Hibbert was paralysed from the waist down and his then-teenage daughter Eve suffered a catastrophic brain injury in the Manchester Arena bombing in 2017. 

They sued self-styled journalist Richard Hall, who claimed the attack was staged by British government agencies without any evidence. 

Here is what we know about the case. 

What happened at the concert? 

The arena was packed with thousands of young people and children for the concert by US pop star Ariana Grande in May 2017.

Many fans held pink balloons and were dressed in cat ears, which had become synonymous with Grande's persona.

As the Nickelodeon star finished her last song, thousands of people started to move towards the exits and the house lights came back on. 

It was then 22-year-old Salman Abedi set off his explosive device which killed 22 people and wounded 59 others. 

He died in the explosion and his younger brother Hashem Abedi was later sentenced to a minimum 55 years in prison for helping carry out the attack.

Videos posted on social media showed fans fleeing the concert screaming and crying, with residents living nearby claiming the bangs were loud enough to shake their apartment.

A public inquiry into the bombing found "serious shortcomings" by venue operators, security staff and police helped the suicide bomber conduct his attack. 

Retired Judge John Saunders, who led the inquiry, said Salman Abedi should have been identified as a threat by those in charge of security at the arena.

What did Richard Hall do? 

Conspiracy theorist Hall has long argued the attack was a hoax and even published a book and videos about the Manchester Arena bombing. 

He also filmed Eve Hibbert and her mother outside their house in 2019 and gave talks which claimed the Hibbert family were not at the concert.

Hall has fought the lawsuit brought against him and argued journalistic investigation did not amount to harassment. 

He said an injunction would be a disproportionate interference with his free speech rights. 

But, Judge Karen Steyn ruled on Wednesday, local time, that Hall's conduct did amount to harassment and said his actions were a negligent and reckless abuse of media freedom.

"Freedom of expression undoubtedly provides protection for journalism which focuses on important occurrences, such as the attack, and investigates the veracity and accuracy of established narratives as to what took place," Judge Steyn said in a written statement. 

"But Mr Hall has abused media freedom. Over a period of years, he has repeatedly published false allegations, based on the flimsiest of analytical techniques, and dismissing the obvious, tragic reality to which so many ordinary people have attested."

Have there been other similar lawsuits? 

This case holds similarities to defamation lawsuits brought against US conspiracy theorist Alex Jones by relatives of victims of the 2012 Sandy Hook school shooting.

Jones has spouted conspiracy theories, from the 9/11 terror attacks being staged to a UN effort to depopulate the world. 

Most notably he claimed the Sandy Hook Elementary School shooting, which killed 20 first graders and six staff members in Connecticut, was a hoax.

He broadcast his theories from his home through his Infowars website and continues to host daily four-hour talk shows online. 

Families of the victims sued Jones on the basis they were subjected to years of torment, threats and abuse by people who believed the conspiracy theories on his show.

Earlier this year, a US judge ordered Jones's personal assets be liquidated in order to pay $US1.5 billion ($2.2 billion) to the families of victims.

What happens now? 

Martin Hibbert said in a statement he wanted the ruling to "open the door for change and to help protect others from what we have been put through".

The Hibberts' lawyer, Kerry Gillespie, said the judgement sent "a very clear message to people who think they have the right to publish absurd, harmful, unfounded allegations against others".

A hearing will take place on November 8 to decide whether the Hibberts should be granted an injunction and paid any damages.