Scotland's former first minister Alex Salmond has been branded "the slipperiest of characters" by , with the ex-PM saying it would have "hurt beyond belief" if Scots had voted for independence.
In his forthcoming autobiography, For The Record, the former Conservative leader concedes allowing the 2014 referendum to take place was a "gamble" - although he said it would be a "much bigger gamble" to dismiss the issue.
After the SNP won an overall majority at Holyrood in 2011, Cameron travelled to Edinburgh to negotiate the terms of the historic ballot.
The former prime minister said: "I went up to Edinburgh for my first negotiation meeting with the slipperiest of characters, Alex Salmond, Scotland's first minister, in February 2012.
"I always used to say you had to count your fingers on the way out of a meeting with him."
Cameron had been at Balmoral for an audience with the Queen in the run-up to the referendum when a shock poll put Yes narrowly in the lead.
Days later, the Queen urged Scots to "think very carefully" about the vote, with Cameron saying he was .
He wrote: "If I were the one who precipitated the end of our island story, it would hurt beyond belief."
Cameron said there was "panic" when the turnout in the referendum - which took place almost exactly five years ago on September 18 2014 - was put at almost 85%, the highest in UK history.
He recalled: "After Clackmannanshire declared at 1.30am with a solitary majority for no, I went to bed but I didn't sleep.
"The lead we were taking started closing overnight. But sure enough, after 4am the No votes kept rolling in.
"Two of the happiest hours of my life followed. Everything was going to be OK."
Scots voted by 55% to 45% against independence, with Salmond announcing within hours of the result being declared that he would be stepping down as SNP leader and first minister.
