Ms Gray has largely finished conducting interviews and is likely to spend the weekend completing her report, which is expected to be factual rather than disseminating blame.
With reports of intimidation against Tory MPs who want to oust Mr Johnson there are concerns that there could be pressure on Ms Gray.
However, Business Secretary Kwasi Kwarteng played down these concerns when speaking to Times Radio.
He said: “She’s extremely well regarded across Whitehall.
“She’s an impressive official, dedicated public servant and she’ll do a great job.
“I think it’s really unhelpful to suggest that there be undue pressure or undue influence exerted on her.”
Mr Johnson will have no more than 24 hours, possibly less, to view the report prior to publication according to The i.
It’s unlikely that he will have the opportunity to feed back to Ms Gray about its contents.
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Mr Johnson claimed that he was unaware that the “bring your own booze” event was against the rules.