As the ink dried on his Anfield contract in August 1977 and another record-breaking cheque was inevitably cashed by the Parkhead powerbrokers, the departure of Kenny Dalglish signalled the end of a golden era at Celtic Park.

Only ten years earlier, his green and white hooped predecessors had blazed a trail around Europe, bringing the ‘Big Cup’ home to British shores for the first time after a spectacular, quintessentially underdog victory against the mighty Internazionale of Milan. In just two years, Jock Stein had worked his own brand of sorcery on this hitherto unspectacular group of footballers and crafted them into the champions of Europe with only the minimum of domestic acquisitions. But as he stood at the pinnacle of European football, Stein already had designs on Celtic’s next generation of home-grown talent.

Milan’s glitterati had grown old and Stein’s Celtic had knocked the twice World Club Champions off their pedestal in breathtaking fashion. These eleven Scottish individuals, who would be known ad infinitum by the moniker of The Lisbon Lions, had certainly served Stein well and he was not about to let them go the same way as Helenio Herrera’s ‘La Grande Inter’.

How do you replace such an iconic captain and leader of men as Billy McNeill, who possessed all the natural qualities of a born winner? Or a winger of such supreme individual talent and panache as Jimmy Johnstone, whose strength and mesmerising dribbling ability bamboozled defences all over the world? Or the commanding and peerlessly influential and talismanic Bobby Murdoch, who could pass the ball with a range and precision that could orchestrate an entire match? These were just some of the dilemmas that faced Jock Stein but the breaking up of this incredible Lisbon Lions dynasty was made a lot smoother by the sheer raft of talent that were waiting in the wings.

Despite the phenomenal success of his team over the previous few seasons, Jock Stein had possessed the foresight to plan ahead and had signed a procession of prodigious Scottish talents, who had been learning their trade from the very best in European football on the Barrowfield training ground every day since their arrival at the club. Inconspicuous young men whose indoctrination into the Celtic way had been gradual and methodical. These young cubs were reared to replace the Lisbon Lions, the most celebrated football team in the history of the Scottish game.

Jock Stein almost simultaneously crafted two football teams in the late sixties and early seventies, that would ensure Celtic could enjoy utter dominance of the Scottish game for virtually a decade. His young collection of reserve team players would experience many talents, triumphs and tragedies throughout the most successful period in the history of Celtic Football Club and he believed they were so capable that he made a proposal to install them into the Scottish Second Division in 1968. Many clubs feared that they would win the league. The Scottish press christened the Lisbon Lions‘ heir apparent, ‘The Quality Street Gang’ and tales of the precocious second string’s successes have become the stuff of Celtic folklore.

During one almost mythical encounter with Partick Thistle in August 1968, and with Celtic needing at least seven goals to win their Reserve League Cup section over Rangers, they ran out 12-0 winners with Lou Macari scoring four goals.

Two months later Scotland’s national team boss, Bobby Brown, asked Jock Stein to supply him with opposition for a warm-up practice match. Stein sent him the Quality Street Gang and the kids destroyed a full Scottish International team, featuring Ronnie Simpson, Colin Stein, Eddie Gray and Billy Bremner, 5-2. Scotland defeated Denmark nine days later.

The 1969-70 Glasgow Cup Final was still a prestigious enough tournament to attract a near 60,000 crowd on a Monday evening and Jock Stein again took the opportunity to showcase some of his finest protégés. A George Connelly-inspired Celtic, with six Quality Street Kids in the line-up, swept a full-strength Rangers team aside and ran out 3-1 winners.

By the time of the 1970 European Cup final, some of the Gang had already forced their way into this great Celtic side and within a few more years many more would become household names. Indeed, many observers believed that the omission of George Connelly from Stein’s San Siro starting line-up had a major bearing on the outcome of Celtic’s second European Cup final in just three years.

The Quality Street Kids were the highest scorers in British football in season 1970-71 and Kenny Dalglish, who hadn‘t yet made his mark on the first team, scored an astonishing sixteen goals in just six games as the reserves wrapped up a League, League Cup and Second XI Cup treble. Their closest rivals, Rangers were defeated three times in just eight days in the League and two-legged League Cup Final. The scores read: 7-1, 4-1 and 6-1.

Kenny Dalglish had scored 43 goals in two seasons with the reserves but his exploits were being monumentally eclipsed by Lou Macari, who netted 91, and the highly-rated Vic Davidson, who scored an emphatic 92. Both Macari and Davidson’s totals also included a spattering of first team goals.

Celtic’s stylish babes were destroying all reserve competition before them and although Jock Stein’s vision of them developing in the more competitive Scottish Second Division had been rebuffed by the SFA, he was at least able to challenge them by regularly staging Lisbon Lions versus Quality Street Gang practice matches at training. Instead of being over-awed by the legendary first-team figures, these cocksure kids fancied their chances and occasionally won the largely-attended bounce games.

So why has the wider football community not heard of the Quality Street Gang? Unlike Sir Alex Ferguson’s extensively lionized class of ’92, many of these underlings to the nonpareil Lisbon Lions capitulated in dramatic fashion and the gang broke up before realizing their incredible collective potential.

Some of the fabled Quality Street Kids went on to become revered throughout the football world with players such as Kenny Dalglish, Danny McGrain, Lou Macari and Davie Hay achieving incredible success for club and country in the seventies and into the nineteen eighties but while the fortuitous few attained incredible glories, there were other phenomenal talents who fell by the wayside in spectacular style.

Scotland’s 1973 Player of the Year, George Connelly, from a small mining village in Fife, walked away from the game at just 26. He had been compared to Franz Beckenbauer and was the natural successor to the seemingly indestructible Billy McNeill but mental illness, alcoholism and a disdain for the limelight drove him out of the game at a lamentably young age.

Tony McBride was a "pocket edition of Jimmy Johnstone" according to Jock Stein but he failed to make a single first team appearance on account of his frequent brushes with the law, much to the annoyance of the taskmaster Stein.

Brian McLaughlin was good enough to break into the first team at just 16. Yet his unfortunate and tragic downfall was prompted by a brutal career-threatening onfield assault in 1973 at the hands of a journeyman Aidrieonian thug, who is remembered for nothing else in the game. McLaughlin had it in him to be the Lubomír Moravcík of his generation but his sparkling career was molested and his grotesque injury literally brought a tear to Jock Stein's eye.

The enigmatic Pat McMahon became Celtic's first post-Lisbon signing and burst onto the scene in the 67-68 season with his Beatlesesque flowing locks and fresh-faced good looks. McMahon was an intellectual, who had trained in the Priesthood as a youngster before moving down to London. Much to his chagrin, he returned to reserve team football after 5 goals in 6 first-team matches and his Celtic career hit the skids. Oddly, he made no further first team appearance and was released after just two seasons.

And there were more. Paul Wilson could be considered something of an unsung hero of the wider Gang as his Celtic career was both lengthy and successful with his place in the club’s history being assured by virtue of his Scottish Cup-winning performance of 1975. Vic Davidson was undoubtedly a player who progressed on a level footing with Dalglish and Macari but only up to a certain point before his career tailed off and his potential was to be eternally considered as unfulfilled. Influential and popular members of the gang, Davie Cattanach and Jimmy Quinn were slightly older and their successes were enjoyed mainly at reserve level. And then there was John Gorman, a player who proved beyond doubt that Jock Stein was wrong to let him go. Not to mention the huge amount of talented young players who didn’t make it for any number of reasons, many of whom may consider themselves as unlucky as they may have succeeded at any other time in the history of Celtic Football Club.

The Quality Street Gang is as much a story about the transformation in attitude from those loyal Brylcreemed round-collared 1960s servants, who encapsulated Jimmy McGrory’s 1950s pipe-smoking discipline, to their floppy-fringed, sideburned superstar counterparts of the 1970s.

By the time of their European Cup semi-final first leg against Atlético Madrid in 1974, Celtic had reached two finals, four semi-finals and two quarter-finals in European competition in just eleven seasons. However, the Quality Street Gang were already fragmenting and Lou Macari had joined Manchester United for more pay in 1973. Davie Hay would follow him across the English border for Chelsea 1974 after going on strike with George Connelly over pay conditions and it wouldn’t be long before Kenny Dalglish left to become the King of the Kop. Celtic fans were left wondering just what might have been had the Quality Street Kids all reached their peak in the green and white hoops of Celtic.

Over forty years on, it is easy to get trapped in time when looking back through the scrap book of a football career which promised so much. The teenage Celtic babes of 1968, who seemingly had the world at their feet when they posed for the baying Scottish press in their green Celtic blazers at Glasgow airport prior to their Italian international youth tournament, may all have had the same destination stamped on their airline ticket on that Summer’s day in May but they would all ultimately travel on vastly different journeys over the next four decades. Some would enjoy the emphatic highs of the game at the very top level whilst others would suffer a far more grim fate in living with the melancholia that hangs heavily over the harsh reality of what-might-have-been.

The Quality Street Gang were brought up by the greatest football team Scotland has ever produced and the result was a group of young prospects who even threatened for a spell to emulate their predecessors. The kids were cultivated on the Barrowfield training ground and the Lisbon Lions passed on the torch so that their successors could continue their incredible forays into the latter stages of European football’s most prestigious tournament. Celtic won nine successive league titles but never reclaimed the honour of winning the European Cup for a second time. If only the Quality Street Kids had all hit their peak together there is no doubt that the Parkhead side would have lifted that glorious prize more than once.

With such a blend of monumental successes, likeable rogues and enigmatic underachievers it is perhaps no surprise that the 2013 Quality Street Gang book is now being adapted for a major documentary film by director, Luke Massey. Celtic and Liverpool fan Massey, on the back of his success with war horror film Armistice, opted for this intriguing group of young footballers as his next project after reading the book over Christmas.

The bittersweet tale of unfulfilled potential has struck a chord with football fans for generations. Many of us can relate to the peculiar, all-too-human idiosyncrasies, which often contribute to the downfall of some of our greatest cult heroes. Icons who threw it all away at the mercy of alcohol, slow horses, loose woman or all of the above, and worse. We seem drawn to these slightly broken characters and their urchinular charms and, once we have become intoxicated by their incredible talents, we always have it in us to forgive their irresponsible ways; we always have another last chance to hand out to them because we know they will always let us down. That's why magnificent players like Robin Friday, Andy Ritchie and George Best became and remain cult icons of the British game. Perhaps we see a human side and fragility to them that we can identify and sympathize with.

Despite the magnificent successes of Dalglish, Hay, McGrain and Macari, as the end credits roll on The Quality Street Gang, Celtic fans will be left wondering, “what if?”

Paul's book is available here, follow him on Twitter here.