When Alex Ferguson announced he was joining Manchester United after eight trophy-laden years at Aberdeen, there was shock among fans.
They had seen the legendary manager lead the Dons to three league titles, four Scottish Cups, the Cup Winners' Cup and the UEFA Super Cup.
One told BBC Scotland News at the time: "I think he's making the wrong move, I think he will regret it."
Ferguson went on to become one of the most successful football managers in history, winning 38 trophies during a 26-year tenure at Old Trafford.
On the 40th anniversary of Ferguson's decision to leave Aberdeen, some of those at the centre of the events have been reflecting on the day.
The story of Ferguson's move to the English First Division on 6 November 1986 was broken by BBC Scotland football broadcaster Roddy Forsyth.
He had been tasked by his editor to head to Aberdeen to find out more about rumours that the Dons boss was in talks with Manchester United.
The flight he boarded in Glasgow was filled with journalists - but most were heading north to cover the Chinook helicopter disaster in Shetland in which 43 people died.
Once in Aberdeen, Forsyth eventually tracked Ferguson and the United chairman Martin Edwards down in an airport hotel.
He had called by chance asking to "speak to a Mr Edwards from Manchester".
The receptionist told him he was seated in the restaurant area.
"I heard some voices and made my way to them," Forsyth said.
"There was Martin Edwards and Alex Ferguson, and I said 'are you the new manager of Manchester United?' and he said 'yes'.
"They had a bottle of champagne which they were drinking and Fergie poured me a little champagne in a wine glass, and I toasted him as the new manager."
After a brief conversation, Forsyth got in touch with his newsroom confirming the story.
"Of course, the normal news led with the Sumburgh disaster, and then the sporting news led with Alex Ferguson," Forsyth added.
"It was a big day for news and sport and broadcasting.
"It was one of these utterly memorable days of your career and your life."
Ferguson had led the Scottish club to a period of success some fans thought would never end.
His departure was met with a mix of anger, disappointment, shock and acceptance.
The views of fans at the Pittodrie Bar were broadcast that day on BBC Reporting Scotland.
One was certain Ferguson would regret the move to the English giants.
"It is a sad case for Aberdeen, and I think he is making a wrong move," he said.
"I think he will regret it in years."
Another said: "Ferguson was preaching about having loyal players. He envied Rangers and Celtic for having that.
"In other words, he was condemning his players for leaving Aberdeen, he has set a perfect example he has just walked out."
Fast forward 40 years and fans today are generally a bit more measured on the whole episode.
Sandy Smith, 72, says he has "seen it all" in a lifetime of supporting the Dons.
"It was totally gutting," he said. "To be fair Man United and Aberdeen - there is no comparison.
"After all he did for the club, I was gutted.
"He had sticky first couple of seasons down there, but he got there in the end."
Ian Donald, the club's vice-chairman at the time, described it as a "shattering blow".
"It happened so quickly virtually overnight," he said in 1986.
"From yesterday morning perhaps having the best management team in Britain we are losing them both."
And it was a lot for the players to take in too.
Captain Willie Miller reflected on the time Ferguson left as a period of "uncertainty".
He thought all players missed the manager once he had gone, despite his famous temper.
"You would not get away with it now," he said.
"It was probably what we expected back then from a manager.
"I do not think the modern day player would accept anything close to it, you know, cups getting thrown around dressing rooms.
"He did not just want to win things, he wanted to win them with style. And it was OK with me.
"I was disappointed to see him go, I must admit, I think everybody was of the same opinion."
Ultimately, it was one man's choice to make and Ferguson made the move, taking his assistant with him.
In his first press conference as new boss he said: "I left probably the most secure job in British football with a life contract at Aberdeen.
"There's only one club that could possibly tempt me away from that and it is the only club I ever wanted to go to way from Aberdeen."
Thirteen Premier League titles, two Champions League victories, five FA cups and four League Cups later - maybe not.
