The brother of a former News of the World showbusiness reporter who died after speaking out about phone hacking said they had "shared a lot of secrets".
Sean Hoare, 48, had claimed his ex-editor Andy Coulson was "well aware" of the practice of illegal voicemail interception at the paper - something Mr Coulson strongly denies.
Mr Hoare, who suffered from alcoholic liver disease, was found dead at his home in Watford in July after he started drinking again to cope with the stress of the attention on him as a phone-hacking whistleblower, his inquest heard last month.
His brother Stuart told the Leveson Inquiry today: "We shared a lot of secrets and I felt very, very strongly that someone had to represent my brother."
He added that he wanted to "let his word still be heard".
When asked by Carine Patry Hoskins, counsel to the inquiry, what he knew of the "dark arts" of journalism, Mr Hoare replied that he did not witness any incidents, but possessed details of them.
He said: "I was fortunate enough to retain certain information that Sean had left with me.
"Sean and I regularly discussed this and there are emails in existence which support Sean's description of a practice referred to as the dark arts."
Mr Hoare told the inquiry into press standards that he had a "special relationship" with his younger brother.
He said: "Sean and I had a very close relationship.
"I think a lot of that was due to the fact we were very different people."
He said that while he was interested in mathematics and sport, Sean "went down the track of drama and the written word".
"We had a very, very special relationship. We spoke probably most days," he added.
Mr Hoare said his brother had told him phone-hacking and another of the "dark arts" known as pinging, where celebrities and people of interest were tracked down through their mobiles, also occurred at The Sun.
"These alleged practices not only went on at the News of the World but it went on at The Sun," Mr Hoare said.
"I want to make it very clear it was a practice that was taken to the News of the World."
He said his brother had initially enjoyed working for the News of the World when he began in 2001 but was struggling to cope in the latter years until he was sacked in 2005.
"Sean, certainly in the last two years of his career with the News of the World, was struggling," Mr Hoare said.
"There was an enormous amount of pressure put on him and other journalists to produce articles that sell.
"He was bringing home work, he was drinking more.
"He was trying to run away from certain issues that were going on at the paper and it wasn't a nice part of his life."
Mr Hoare said his brother told him it did not matter whether a story could be stood up or not as long as they were delivered.
"He got carried away like a lot of journalists did but they were under a lot of pressure from seniors to deliver," he said.
"I doubt in my own head that he realised he was doing wrong.
"I think he thought he was producing, he was getting the stories, he was getting his name on the front page, his ego was being stroked."
He said his brother had never hacked phones but had witnessed it.
Last year, he said his brother had left journalism and was working with horses.
"I think being away from journalism gave him the ability to step back and understand what was right and what was wrong," he said.
"In the entertainment world, for Sean to do some of the jobs and gain some of the interviews and gain the friendship of certain people, Sean thought he had to be like them."
He said his brother had abstained from drugs and alcohol for about eight months but began drinking again in the last few months before his death.
The inquiry also heard evidence from Independent on Sunday deputy editor James Hanning.
He had several conversations with Sean Hoare about journalistic techniques at the News of the World.
Mr Hanning said the information he gave him was off the record, but he had since agreed with Stuart Hoare that he should disclose what was discussed following Sean's death.
He told the inquiry: "I gained interest in the whole story three or four years ago and it was really when I met Sean that I was able to sort of push things on a bit.
"It had been a longstanding interest of mine. It just struck me there was something going on."
He said he first met Mr Hoare in summer last year, after which they met a further "four or five times".
When David Barr, counsel to the inquiry, asked the witness if Mr Hoare told him he had hacked phones while at the News of the World, he replied: "Yes, he did."
He went on to say that it happened "numerous times", and that "a number" of other people at the newspaper hacked phones.
Mr Hanning described one incident involving a celebrity and other employees at the newspaper.
He said: "A famous female celebrity rang a senior executive on the paper and said 'I understand you may need to get in touch with me, this is my PA's number'.
"And the female celebrity handed over the number to this senior executive and they had a chat and he put the phone down and he then passed the note on to another executive and said 'There you are, there's X's number, tell him to get hacking'."
Mr Barr asked if he thought Mr Hoare had been drinking around the time of their first meeting.
He replied: "I'm pretty sure, as far as I can be, that he wasn't taking drugs.
"Whether he was not drinking, I was less certain. He may have had a half of lager or something, but there was certainly no evidence that he was in the state that I heard he had been in the past."
He added: "I have no feeling that his memory was impaired at all."
Mr Hanning said Mr Hoare was "wounded" after being sacked by the News of the World.
"He was aggrieved because - as we have heard from his brother - he loved journalism. He loved the game," he said.
"I think he did feel wounded and, you know, the boat was moving off without him, as it were."
He went on to say that Mr Hoare claimed he had been offered £60,000 to sell his story, but he did not ask for any money in return for speaking to journalists.
Mr Hanning said that although he was "the one I spoke to most", he did contact "one or two" other employees at the newspaper to corroborate what Mr Hoare had told him.
Mr Hanning also told the inquiry that the News of the World paid someone at another newspaper for a list of the stories they were working on.
He said: "For a rival paper to get hold of your news list, it's a good thing to have.
"I'm told - Sean told me - that they would get £400 in cash and a person on another paper was paid £200 to hand over this news list.
"£100 would go to Sean and £100 would go to the other executive."
Former News of the World sports reporter Matt Driscoll, who made a successful employment tribunal claim for disability discrimination after he was sacked by the News of the World, told the inquiry how a tip he had received which claimed Sir Alex Ferguson had health problems led to the newspaper "blagging" the Manchester United manager's medical records.
He said he had telephoned his football contacts but was unable to confirm the story.
"In the end I had to go to my sports desk and say I really don't think I can get any further forward with this," he said.
Mr Driscoll went on: "My sports editor said, 'leave it with me, we'll see what we can come up with'.
"And then I'm pretty certain - as I said in my tribunal - it was that day I got a phone call saying, 'you're absolutely right with the story'.
The witness said that the newspaper had obtained Sir Alex's medical records. He told the inquiry that this was often done by sending a fax to a hospital claiming to be a specialist in need of confidential information.
The number of times that technique worked was "incredible", he added.
Mr Driscoll said Sir Alex was contacted about the story, and since the medical issue was not serious, a deal was done between both parties.
"I think there was a phone call to that football manager to tell him exactly what we knew and that he was very upset about it and he made his thoughts known about that and said that there was no way he wanted that story to appear in public."
He continued: "It was put to Alex Ferguson that we wouldn't use this information."
[In return] "he then started co-operating with the paper" [and gave them stories].
Mr Driscoll worked for the newspaper from June 1997 to April 2007. He had previously worked for the Daily Star.
"When I was there the Daily Star had a very small budget compared to the rest of Fleet Street," he said.
"They could not really afford to spend a lot on news gathering and certainly the use of any of the dark arts as they now seem to be called, the Daily Star wouldn't have been able to afford that even if they wanted to."
Mr Driscoll said he had no knowledge of private investigators being used by the News of the World.
He said journalists never questioned the ethics of techniques used or their editors' decisions.
"The editor can make you look very good and he can also make you look very bad," Mr Driscoll said.
"He decides who gets the tips, who gets the stories to work on.
"He also decides whether your copy gets in the paper or not."
He said he went from being hailed a very successful journalist to being told he was unsatisfactory.
He said despite there being no evidence that he was under-performing, once an editor decides "your face doesn't fit any more", the journalist's time is up.
Mr Driscoll said the employment tribunal had "finished" his career in journalism because he was seen as "the guy who's taken on the bosses".
He also said he had received an anonymous email which claimed his mobile phone may have been hacked.
He told the inquiry that he had contacted police, who said there was no initial evidence but they would get back in touch with him at a later date.
Mr Driscoll, who was diagnosed with depression, said his illness was "entirely" down to working conditions at the newspaper.
"I was a fit and healthy person until 2005," he said.
He also denied that he had an "axe to grind" against his former employer, and claimed he was simply "unhappy" that journalists were being forced to take the blame for the phone hacking scandal.
The inquiry was adjourned until tomorrow, when it will hear evidence from Piers Morgan, the former Daily Mirror and News of the World editor-turned CNN interviewer. He will appear via videolink from the United States.
Prime Minister David Cameron set up the Leveson Inquiry in July in response to claims that the News of the World commissioned a private detective to hack murdered schoolgirl Milly Dowler's phone after she disappeared in 2002.
The first part of the inquiry, sitting at the Royal Courts of Justice in London, is looking at the culture, practices and ethics of the press in general and is due to produce a report by next September.
The second part, examining the extent of unlawful activities by journalists, will not begin until detectives have completed their investigation into alleged phone hacking and corrupt payments to police, and any prosecutions have been concluded.