Willie Cunningham is celebrated as one of the heroes of Northern Ireland's 1958 World Cup Finals, but perhaps his biggest legacy is as a key mentor to Sir Alex Ferguson.
Born years apart in different lands but seemingly cut from the same cloth, these two imposing characters could be genial one minute and fiery the next.
Sir Alex's notorious 'hairdryer' treatment was modelled on his former Dunfermline boss, whose iron-fist-in-a-velvet- glove approach was to be the hallmark of Fergie's managerial style years later.
Roy Barry had a ringside seat when their larger-than-life personalities exploded on an unfashionable Fife club during the height of the Swinging Sixties.
Dunfermline were going toe-to-toe with the Old Firm and had just come within a point of taking the League title. They would go on to win the Scottish Cup in 1968 with Barry as captain, though Cunningham had just left the club by then.
"Those were fantastic days with Sir Alex and Big Wullie - two of the biggest, colourful characters," says Barry, who also played for Edinburgh rivals Hearts and Hibernian and captained Coventry in the early 1970s.
"They were both volatile and committed but also had hearts of gold. Big Wullie could have you running through a brick wall for him and Sir Alex clearly had that kind of loyalty too.
"Sometimes that clash of character can lead to trouble and they both had their fair share of fall-outs, but there was a mutual respect."
Barry was no shrinking violet himself, having a hard man reputation of his own that saw him effectively hounded out of Scottish football after falling foul of the authorities.
He came to blows with Fergie on the training ground just days after joining the Pars from Hearts in 1966, but it was their Mallusk-born boss who had the final say.
"I didn't want anyone to think they could bully me and ended up coming to blows with Sir Alex," recalls Barry, who is a sprightly 77 years old. "Big Wullie sent us both off and told us to go to the hut, which was our changing room.
"We sat there like naughty schoolboys in a headmaster's office talking about what was going to happen to us. After training, the door burst open and standing there, like John Wayne, was Big Wullie. He had hands like mitts and was spitting into both of them.
"He rolled up his sleeves and stood in a boxing stance. There is a picture in the old boxing magazines where the fighter has his fists raised and that image with Big Wullie's head on it is seared on my brain.
"Alex and I were petrified. Big Wullie said, 'Right, you want a fight? Who's first?' And both Alex and I bleated out at the same time, 'Not me, boss'.
"I have known Alex for a long time and have never seen him as intimidated by someone or something as he was by Big Wullie then."
Ferguson is notorious for his in-your-face combative style in the dressing room and the 'hairdryer' was coined by his Manchester United players during the 1990s to describe how it felt to be on the receiving end.
There is no doubt that Big Wullie finished up in the Old Trafford dressing room, in spirit at least.
Last week, 11-time Premier League winner Paul Scholes recalled how he was the victim in one such outburst after a 4-3 defeat at Newcastle in 2001 and admitted it was a frightening experience.
Little does Scholes know that Fergie's 'hairdryer' had 'made in Northern Ireland' imprinted on it.
"Big Wullie was the original hairdryer," adds Barry. "It came from him.
"He would come up to you and just shout in your face. You would feel the hot air from his breath ruffle your hair, for those of us who had any.
"He didn't need to throw cups of tea at you because he was more vocal. You would shudder with some of the things he would say and the way he said it.
"We were used to being spoken to like that. People would be in your face more. If they had a point to make, they would tell it to you straight and not behind your back.
"Big Wullie would dish it out to every one of us at some point, including Alex, and we all took it because we understood a hard way of living.
"We were all working-class lads. My background was as an apprentice welder in the Leith shipyards and Alex was brought up in the shadows of the Govan shipyards and worked as an apprentice toolmaker.
"Nowadays, I guess some managers would be taken to court for doing some of the things that went on back then."
Cunningham, who died in 2007, didn't just rely on a carrot and stick approach but earned respect for his knowledge of the game.
He had one of the great teachers in Jock Stein, his manager during his playing days at Dunfermline.
Stein deployed him as the first ever sweeper in British football, helping the Pars to Scottish Cup success in 1961 - with Cunningham the only non-Scot - and some great European wins, including over Everton in the Fairs Cities Cup.
"Willie also had a great tactician's brain and that appealed to Alex, who was eager to learn," adds Barry.
"He encouraged his full-backs to overlap and that was something not really seen before.
"When Alex used overlapping full-backs as part of that great Manchester United team in the 1990s, I remember thinking that came right out of Big Wullie's playbook.
"There is no doubt that Big Wullie finished up in the Old Trafford dressing room, in spirit at least."
It was perhaps fitting, therefore, that when Ferguson was looking for his first break in management, it was Cunningham who should provide it.
The Northern Irishman recommended Ferguson as his successor at St Mirren in 1974 and never looked back.
"They had tremendous respect for each other and did get along when they weren't mouthing off," says Barry. "I guess Willie saw more than a hint of himself in Alex."
Barry and Sir Alex have continued their friendship down the years and the Old Trafford great even filmed a video of reminiscences that was shown at a Dunfermline 'This is Your Life' tribute night for Barry.
Barry remembers one frightening anecdote that reveals how Sir Alex's managerial career nearly floundered on the rocks below the Forth Road Bridge.
"Alex was coming across to Edinburgh with me after training," he says. "We had some time off and Alex was staying over at my house in Edinburgh.
"We both ditched our cars at the training ground and got a lift back from our reserve keeper Davie Anderson, who also lived in Edinburgh.
"We were on the hump of the Forth Road Bridge when Davie had a seizure and slumped over the steering wheel.
"The car was freewheeling from side to side with Alex panicking in the front and me panicking in the back. He shouted, 'Drive the ******* car' and I blasted back, 'You drive the ******* car, you're in the front'.
"I then found myself hanging over poor Davie's head trying to steer the car until Alex managed to apply the brake just before we reached the toll booth.
"We had to call an ambulance for Davie and, while he made a full recovery, it did spell the end of his career.
"Whenever Alex and I meet up at social gatherings, it is a story that always comes out, but only after a few stiff drinks."