The Crown Unmasked series precipitated three separate inquiries into Crown’s activities in Victoria, NSW and WA, a finding that the company was unfit to open its new casino in Sydney, and Packer’s decision to finally cash in his chips with private equity firm Blackstone.

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The most serious allegation put forward by Packer in the reported emails was that Costello worked for him in 2011 as an undeclared lobbyist to curry favour for Crown Resorts from the newly elected Baillieu government. This was rejected on Monday by Costello, who says he provided financial advice to Packer’s company Consolidated Press Holdings but never lobbied on its behalf.

Costello’s denial is consistent with the recollections of Victoria’s gaming minister at the time, Michael O’Brien, who said emphatically: “Costello has never, ever lobbied me on behalf of Crown or anyone else.”

In a series of answers to further questions, Costello said he provided financial advice to CPH in 2011, when he was working for himself, and that his contract ended in 2012.

This timeframe coincides with Costello becoming a partner in Epstein Costello Gazard (ECG) Advisory Solution, a registered government relations firm, but the former federal treasurer insists he was only an investor in ECG and not a lobbyist.

Another senior figure at ECG confirmed that neither Crown nor CHP were ever clients of the firm.

Costello joined the board of Nine in 2013. He was appointed chairman of the media company in 2016. Nine Entertainment is the owner of The Sydney Morning Herald and The Age.

Packer’s attack on Chessell came after Chessell stopped replying to what he described on Monday as a “blizzard of correspondence”.

“After trying to engage with him at first – which clearly didn’t work – I’ve ignored almost all of it,” Chessell said in a note to staff at The Age and Herald.

Chessell is not the only person to sever communications with James Packer in recent weeks.

The Age and Herald are aware of another prominent figure who sought the advice of technical experts to stop Packer’s missives from reaching their inbox. As they explained: “One minute the sun shines on you but for whatever reason, it can turn. You come back and your device will be smoking.”

Packer’s email circle includes American film producer Brett Ratner, investment banker and corporate adviser Matthew Grounds, Nine personalities Karl Stefanovic and Peter FitzSimons and executives, broadcasters and journalists across rival commercial networks.

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It also includes people who aren’t accustomed to their names being cc’d alongside those of journalists.

The most remarkable thing about Packer’s emails is that they took so long to become public. Some of the recipients explained that, in light of what Packer has said about his mental health and decision to stop taking medication, they were more concerned at the tone and volume of the emails than the contents. Many of them went unread.

The Packer family owned the Nine Network between 1956 and 2007. James sold the then television company to private equity firm CVC for about $5 billion.

In his note to staff, Chessell said that throughout the research and production of the Crown Unmasked series, Costello never spoke to him about it.

“I received another dozen emails from Packer last night. In the past, he has copied in executives from competitors such as Seven and News. I hope he genuinely does make peace with Crown Unmasked and I wish him all the best.

“As executive editor I backed Crown Unmasked to the hilt, pushed for it to be a co-pro with 60 Minutes and backed our robust defence of those stories when Crown launched an (ultimately failed) PR campaign (supported by News Corp) to discredit us.

“No other newsrooms would have had the courage to run Crown Unmasked. Certainly not The Australian.”

On this, Packer agrees.

“Crown Unmasked was a great story and Nine should be very proud of Crown Unmasked. Well done to all involved. I mean that”, Packer wrote in one of his emails.

“I will always be ashamed that some of the bad things that happened at Crown happened on my watch. I regret all that a lot and am trying to do better in my Act 3. Nick McKenzie definitely knew more about what was really happening at Crown than I did. My bad obviously and I have deep regret about my shortcomings as Crown chairman.”

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