NOSTALGIA can play tricks with the mind. Loyalty can similarly alter perception. John Clark admits to being influenced by both but not to the extent that either clouds his thinking. When he declares Jimmy Johnstone to be Celtic’s greatest ever player, he does so with an obvious fondness for a former team-mate and friend but also with the clarity of judgment that stems from having worked alongside so many who have followed in Johnstone’s footsteps.

Now 75, Clark, one of the club’s fabled Lisbon Lions, is still to be found inside Celtic’s Lennoxtown training ground most days, helping with the kit and enjoying the changing room chatter. Hundreds, possibly thousands, of managers and players have poured in and out of the door on his watch. Many have heard Clark’s anecdotes about Johnstone, the fleet-footed winger who graced Celtic’s colours more than 500 times over a dozen years. Some, like Martin O’Neill, have made special requests for an audience and then sat enraptured as tales unfolded of the man known universally as Jinky, his on-field prowess and off-field capriciousness. Clark has enough stories to more than fill a book but, unlike many of his former team-mates, will not be committing them to print. “That’s not for me,” he admits.

On this occasion, however, he is happy to delve into the memory banks once more. A documentary, produced by award-winners Purple TV, on Johnstone’s life will air on BBC Alba this Friday and footage of Clark features prominently throughout. A decade has now passed since Johnstone died aged 61 but the recollections still come easily.

“It is always emotional talking about Jimmy, your friendship with him and growing up with him in football,” admits Clark. “Away back when I was at school - and I was that bit older - his name was always getting mentioned through his ability and performances in schools football. People kept on talking about this Jimmy Johnstone, but I’d never met him until he came to Celtic.

“If wee Jimmy was playing just now I don’t think any coach would be able to change the way he played, that unique style. He just had it. His skill alone was unbelievable. He was one of those boys, if he beat you he’d want to do it again and again. Jimmy’s control of the ball was exceptional. If he was playing now he’d be a superstar. It was a different era, of course. But you can’t change the skill of a person, can you? If he’s got the ability and the skill, it will always be there.”

How good Johnstone was - as with any player who ever kicked a ball – is, of course, entirely subjective. Clark, though, places him higher than Henrik Larsson in the pecking order of Celtic all-time greats, and believes he may be the closest thing Scotland has come to producing anyone of the calibre of Lionel Messi.

“I’m biased because I played with him but I have to say Jinky is Celtic’s greatest ever player,” he says. “I think he just shades it. Henrik might not like that right enough! Body-wise, Jinky was a strong guy. Height-wise, well you look at Messi just now in the modern game, Diego Maradona even, then Jimmy was the same. His ability and skill, it was just incredible. He was our Messi back in the day. Jimmy could do anything with a ball. With a ball at his feet, I don’t think Jinky would be second to anybody.

“I like the guys you can say to 'on you go and dribble'. It gets people off their seats and they feel like they’re being entertained. The boy [Partick] Roberts at Celtic is a bit like that. He’s quite prepared to take people on and the fans like watching that. But I don’t think there’s too many like Jinky in Scotland. Ach, there’s nobody in Scotland like him.”

There were off-field problems, too, with Johnstone’s behaviour often exasperating manager Jock Stein and almost certainly contributing to the player being released by Celtic in 1975.

“A lot of things happened back then that you don’t always know the reason for,” said Clark. “I doubt it was anything to do with Jinky’s skill or anything like that. Sometimes your time’s up and that’s it. That hurt him. That was tough for him to take.

“I dare say there was another side to his nature. He maybe sometimes did things you wouldn’t do yourself but he was a great guy to have in your corner. He always liked a laugh and a song when it was a social event. He lit up a room. He had such a big personality. Certain people just have that presence about them.”

- Jimmy Johnstone, produced by the award winning purpleTV, will air on BBC ALBA, Friday 30 September at 9.30pm.