If Jock Stein were to happen upon Celtic Park this afternoon it might take him a minute to find his bearings. The sober entrance has been replaced by glorious colour, a celebration of the essence of what can be revealed inside.

And yet amidst the modern face of the Parkhead club, Stein would not have to venture far to find his DNA firmly embedded into a club for whom his name casts a shadow over all who have followed in his footsteps.

Anyone under the age of 50 will not have seen Stein’s greatest accomplishment other than on a screen. But even today there is not a Celtic fan over primary school age who does not know the influence of Stein, with his name synonymous with the highest point the club will ever reach.

As one esteemed colleague once observed in print, 1-9-6-7 is the code that quells house alarms and opens bank accounts, its numbers tattooed onto the psyche of a support who are still reverential, 50 years later, to the finest hours in Celtic’s rich history.

Celtic were the first British club to win the European Cup, and still the only Scottish club to have reached the final. Celtic are one of only three clubs to have won a “quintuple” the others being Barcelona (2009 and 2011) and Inter (2010). The company they are keeping tells its own story.

Stein’s observation that Celtic reached those heights by playing “pure, beautiful, inventive football” has resonated through the game ever since, with the free-flowing, attacking style the blueprint from which many others followed through the decades.

He might have recognised some of his own philosophy today watching the swashbuckling style of a Barcelona – without the sideshow shenanigans, of course – and certainly in Celtic’s dismantling of the fabled defensive Catenaccio style of Helenio Herrera’s Inter Milan side, the Parkhead club paved the way for a different kind of football, with energy, fluency, penetration and creativity its heartbeat.

One can only wonder what Stein might make of the Celtic Way, of the bronze statue of himself that adorns the entrance to the now modern stadia and the montage of accomplishments, old and new that wrap themselves around the façade of the club.

But while the landscape that he knew has changed, time has not altered the hue of Celtic’s 1967 triumph but rather framed the moment as the pinnacle to which everything else will forever be in its slipstream.

Such has been the vast economic changes within the game in the last two decades that the European Cup itself would feel like a venture into a foreign land for Stein today. Players hailing within a 30-mile radius of the club? Making up a modern-day squad at the highest level with 30 different nationalities might be more in keeping with it.

If the star that sits astride Celtic Park or the star is not enough of a visible reminder of just where this club have been, one does not have to venture too far to hear a first-hand account of that day in Lisbon in May, 1967.

John Clark, the kit director now at Celtic Park, epitomises the humility and dignity of a squad who will be unsurpassed in terms of their achievements to time immemorial at the club. It would be wrong to suggest Clark and his colleagues are dismissive of the achievement but nor are they out of touch with what it meant to those around them.

For all the adulation that has followed them, for all the attention and repetition of stories and anecdotes, it is a tale that has never grown tired, not for the ears that it falls on or the tongues from where it comes. The Lions as a collective remain charming, humble, eager to please and forever engaging to an audience for whom they represent what it is to be Celtic.

How many times might Bertie Auld tell of singing The Celtic Song in the tunnel as Stein’s side walked out of the dressing rooms and prepared for the biggest night of their lives, or how many times might he hold a room in the palm of his hand as he charts what it was like for a group of milk-bottle Scots to line up against the movie-star looks of the Italians, with their oiled hair and tanned limbs? The jokes of Ronnie Simpson and his false teeth getting lost in his bunnet which he kept behind the goal as fans poured onto the pitch will raise a laugh whenever it is told, one of many tales that will be passed on through different generations.

There will always be a captivated listener, these stories immortalised and woven into the fabric of the club, ensconced in that little gold star woven above the club crest and exactly what it represents.

Theirs was a triumph of will, of spirit. Of the underdog coming to the fore and seizing the moment, their achievement crystalised forever in the sunshine of Lisbon, in the determination of the comeback and the sheer courage in how they played their football.

Today we laud the modern full-back, their fitness levels, their aggression, their manner of linking play from back to front and yet it was there, in Lisbon, 50 years ago when Tommy Gemmell encapsulated those ideals. Gemmell scored not just in the 1967 final when he levelled to cancel out Sandro Mazolla’s penalty before Stevie Chalmers scored the winner, but again in 1970 when Celtic lost to Feyenoord. Let that sink in for a moment.

The 2-1 scoreline in Lisbon could well have been more; the stats show that Giuliano Sarti, the Inter Milan goalkeeper, made 13 saves as Celtic destroyed the Italians’ defence with their incessant forward play.

And if the landmark celebration of making it a 50-year anniversary is a chance to pay homage once again to that, but it is not a moment without its solemnity; Gemmell’s passing earlier this year casts a shadow over the party this month, while Bobby Murdoch, Ronnie Simpson and Jimmy Johnstone will all have more than one glass raised to their honour this week. Billy McNeill, the first British man who got his hands on the European Cup in the Estadio Nacional on that glorious marble terrace, was a formidable presence. The authority with which he commanded himself not just on the park but how he carried himself off it too makes his illness that he is fighting all the more unpalatable to those who revered him at his peak.

This week, though, is about celebration, about applauding the finest moment in the history of the club and lauding those who put Celtic firmly at the front and centre of European football, with their reputation for attack there for all to follow.