In comments that the BBC later reported
had displeased Buckingham Palace,
Cameron told the public broadcaster
that he sought help from the Queen's private secretary before the vote, amid "mounting panic" that Scotland would decide to sever its union with England and Wales.
The former PM had said he was "not asking for anything that would be in any way improper or unconstitutional," during the BBC documentary marking the publication of his memoir "For the Record."
"But just a raising of the eyebrow, even you know a quarter of an inch, we thought would make a difference," Cameron said.
And that appears to be what the Queen did. Days before the vote, she said she hoped people would "think very carefully about the future," in what was seen as a warning to Scots considering voting to leave the union.
The comment, made to a well-wisher while leaving a church service near her Scottish holiday residence Balmoral, was splashed across British newspapers at the same time polls were predicting a nail-bitingly close result.
The Queen's comment marked a rare intervention on the political stage for the monarch, who is supposed to remain neutral
And it certainly didn't hurt the No campaign -- which ultimately won the referendum to keep Scotland inside the Union.
Current Prime Minister Boris Johnson said he would not be drawn into his predecessor's discussions with the Queen, the UK's Press Association (PA) agency reported on Thursday.
"Not only do I not comment on conversations that I may have held with Her Majesty, but I don't comment on conversations she may have held with anybody else," Johnson told reporters, according to PA.