Just a few days before the Scottish Independence referendum in 2014, a secret public opinion poll caused "panic" among No campaigners, a new documentary statement.
He states that an internal survey conducted for the British government has given the campaign Yes four percentage points ahead.
Also in the document, BBC veteran broadcast Allan Little criticizes the attitudes of some of his London colleagues to independence.
BBC chief Ken MacQuarrie said the company did their job professionally.
"Did something changed"
The third part of the documentary series Yes / No: Inside Indyref, which will be shown on BBC Scotland on Tuesday, you will see the last days of the campaign in 2014.
Campaign Well eventually won a referendum by 55% to 45%.
Better Together, who fought for Scotland to remain part of the UK, launched a two and a half year campaign in polls up to 20 points.
But as the September 18 election day approached, the result was too close to calling.
Douglas Alexander, who was Labor MP and senior Better Together, says "something has moved".
According to Andrew Dunlop, Special Advisor to Prime Minister David Cameron, the government was so concerned that it was conducting its own daily survey.
On Friday, September 5, less than two weeks before the election, his secret results showed that the leadership of the Yes campaign was four points.
It came on the same day as YouGov's vote was taken by Sunday times to show Yes was the poll's leadership for the first time by 51% -49%.
According to Ruth Davidson, the leader of the Scottish Conservatives, there was a "great panic" from everyone who was involved with Better Together.
Despite the fact that Mrs Davidson advises everyone to "keep your living nerve", plans have been prepared at the highest level to completely change the campaign's approach.
George Osborne, who was then Chancellor, continued on Sunday morning's Andrew Marr TV program to announce an action plan that would give Scotland more powers in the areas of taxation, spending and welfare.
The documentary also spoke with Nick Robinson, who was the BBC's political editor at the time.
He had a high-profile dispute with Alex Salmond, who was the first Scotland minister and leader of the SNP at the time, despite his plan reporting by Royal Bank of Scotland to move his headquarters to England in case of a yes vote.
The couple engaged in a long exchange during a press conference and Robinson claimed in his news report that Mr. Salmond did not answer the question.
Robinson said to the Yes / No program: “In the end, it was a subjective view of whether he answered the question correctly or not.
"It wasn't a clever script line. In truth, if I got a chance, I'd rewrite it."
BBC Allan Little, who grew up in southwestern Scotland and worked for the corporation for more than 30 years at the time of the referendum, told the program that she was surprised at how few people in London knew about what brought Scotland into that moment.
The Little, who was a BBC referendum officer, said: "I know how hard my colleagues work in London when they try to get the right thing.
"It's in DNA when you're a BBC journalist."
"I am not cynical, but I was quite surprised that some of my colleagues did not understand their own assumption that Yes was wrong."
He added that some colleagues thought that "our responsibility was to produce a series of pieces to show how stupid it would be to vote Yes".
Ken MacQuarrie, who was director of BBC Scotland, told the BBC program he "left" his own opinions in reporting.
He said, "People did professional work as much as possible in every situation they encountered."
Yes / No: Inside Indyref on Tuesday at BBC Scotland at 22:00 and all three episodes will be available on BBC iplayer.