Lou Vincent has not been granted immunity from prosecution in return for giving evidence against Chris Cairns.
The 36-year-old stood in the dock at the Southwark Crown Court as the first witness in the trial against Cairns, whom he described as an "icon", on charges of perjury and perverting the course of justice.
Before Vincent started to give evidence, Mr Justice Sweeney warned the former cricketer that he was under no obligation to say anything which might incriminate himself and put him at risk of prosecution.
"Because I anticipate you're going to be asked about various potential criminal offences, it is my duty to advise you of the privilege against self-incrimination," said the judge.
He cautioned Vincent that he did not have to answer questions which might incriminate himself of crimes committed in the United Kingdom.
Vincent asked for an example to clarify the situation, then simply said: "I understand".
Under questioning from Crown prosecutor Sasha Wass QC, Vincent opened his evidence by confirming he would be talking about match-fixing in cricket and then immediately accused his former "icon".
"I was involved in match fixing under the direct instructions of Chris Cairns."
Vincent explained to the jury about his role as a batsmen in the New Zealand team where he was "star struck" by Cairns, whom he described as a match winner with an "amazing aura" of a champion.
After his international career ended, Vincent said he had his first bout of depression, which was a "major mental meltdown" and he turned to cannabis to help deal with his state of mind.
He said he was "excited" to sign a $US350,000 contract with the Chandigarh Lions in the Indian Cricket League, where Cairns was the captain.
Within a week, he was offered a "sponsorship deal" and agreed to meet an Indian man "Mr Gandhi" in a hotel room.
When Vincent turned up to Mr Gandhi's room, there was a woman sitting on the end of the bed which the man described as a "present" for sex and a "big wad of cash".
That's when the "penny dropped and alarm bells rang", said Vincent.
The man would not let him leave without the cash, so Vincent told him to leave it in the safe.
At that stage, Vincent said he was not interested in being corrupted. As soon as he left the room, Vincent went to the room of his agent Leanne McGoldrick who represented a number of other New Zealand cricketers.
Vincent wrote down the code for the safe for McGoldrick and she said she would "take care of" reporting the approach.
He explained the ICL tournament was unsanctioned by the International Cricket Council and was very unorganized, so there wasn't any formal reporting lines for corruption.
"It was like a bunch of mates going to the park and playing cricket, but on telly."
So Vincent did not take the match-fixing approach any further, but had an informal chat with the ICL chairman Tony Greig at a hotel bar.
He said he then visited Chris Cairns to talk about what had happened.
"Chris was obviously interested and then there was a pause, for a short period of time, then he turned to me and said: 'you've down the right thing'.'
"'Right, that's good cover. You're working for me now'."
The conversation quickly turned to match-fixing, Vincent, and how each of them could get a "piece of the pie."
Vincent said he was shocked but then felt a "sense of belonging" during a time of his mental health problems.
"I felt like I'm part of the gang, I'm involved in something which is obviously out there...I'm under Chris' wing and I'll never have to worry about money again."
Cairns sat in the dock with his arms crossed as his former team mate walked into the witness stand, then listened intently and took notes while he spoke.
Earlier in the morning, Lou Vincent walked confidently into the Southwark Crown Court hand-in-hand with his wife Susie Markham to face his former friend and idol.
Asked how he was feeling before taking his seat in the witness box, he replied: "First in to bat, hope it's a green one".
By that, if Vincent was hoping to give evidence quickly and get out - it's very unlikely.
The former opening batsman is the principal witness for the Crown, as someone who has confessed to match-fixing and directly accuses Cairns as the one pulling the strings.
Once he has given evidence for the Crown, the Queen's Counsel representing Cairns will have his turn to cross-examine Vincent.
His trouble with depression, alcohol and cannabis have already been raised in court and will be a likely target for Orlando Pownall QC to question him on.
Vincent also accused his former Black Cap team mate Daryl Tuffey, who also played for Chandigarh, of match fixing.
"I have no hesitation saying he was involved," said Vincent.
He said there were six or seven players at Chandigarh who were underperforming, including Dinesh Mongia who was another former international.
- Jared Savage in London