TVNZ public affairs manager Glenn Sowry last night would not disclose who, apart from Mr Swain and a Wellington TVNZ executive, was present in the TVNZ box.
But Herald inquiries later found that Dr Armstrong's guest list featured key New Zealand figures, including TVNZ presenter Paul Holmes and his partner, Deborah Hamilton.
On the Armstrong list were also US Ambassador Charles Swindells and his wife, and Economic Development Minister Jim Anderton and his wife, Carole.
Also in the box were Kristy McDonald, QC, and her husband.
Mr Swain yesterday confirmed the meeting, but said he could not recall all present.
When prompted, he said he did remember meeting Kristy McDonald, who has worked closely with Dr Armstrong and was expected to provide policy, strategic and legal services to Dr Armstrong's big-business advisory group.
He confirmed Holmes and Mr Anderton were also in the box, but said his "loose" meeting only involved Dr Armstrong.
"It was a very, very brief discussion.
"He said he was getting [former Australian Prime Minister] Paul Keating over from Australia - he had been over there in the last couple of weeks."
Mr Swain said he agreed to meet Mr Keating, whom he had long admired.
It was agreed that it would be beneficial for Mr Swain to "sit in on" the meeting in Dr Cullen's office last Thursday.
Mr Swain said he had not known before the meeting that a group was being formed by Dr Armstrong, and he had not seen any papers.
Dr Armstrong, who leaves his job as TVNZ chairman on Monday, presented Mrs Anderton with a blanket matching Canterbury's colours at the end of the function.
Last night Paul Holmes confirmed his presence:
"It was the first time I had been invited to the corporate box for years. I thought it was a most interesting little crowd.
"Paul Swain was the surprise - I couldn't figure out where Paul came into Ross' orbit. I went away smiling thinking, 'Why was Swain there? What's Ross up to now?"'
Asked how often Dr Armstrong had used TVNZ's Wellington corporate box, Mr Sowry said "possibly four or five times" since it was acquired in June.
"Basically it was a regular hospitality opportunity at the box. They are always co-hosted, if the chairman's in attendance, by an executive."
He said TVNZ's Wellington head of sales, Warren McDonald, had told him who his guests were.
"But beyond that I don't know who was there. We're not really in the habit of giving out names of who the guests are."
Dr Armstrong was forced to resign his two state chairmanships on Monday after a paper sent to industry leaders was leaked.
The paper, which Dr Armstrong accepted was his responsibility even though he did not write it, implied that businesses could get the inside track on public-private infrastructure projects (PPPs) and make useful political contacts if they joined his group.
Dr Armstrong has said that that was a mistake and it was not his intention to give anyone an unfair advantage.
The letter that offended the Government:
Pacific Road NZ: Infrastructure Partnership Between the Government and the Private Sector