The Sean Fallon you will read about in today's obituaries is the devoted Celtic servant, the faithful right-hand man and fearless player.

Delve into any Celtic history and, accompanying his name, you'll see the same adjectives: "reliable", "honest", "solid", "wholehearted". And it's true that he was all of these things. But he was also so much more.

Over the past year, I had the privilege of working with him on an autobiography. Even before taking a single note, I considered his to be the great untold Celtic story and Fallon to be one of the club's most influential and undervalued figures. I'll admit now that I didn't know the half of it.

I was aware, of course, that he had scouted and recruited several Celtic greats, and that all but one of the Lisbon Lions had been in place by the time Jock Stein arrived. I'd heard the famous story of him leaving his wife in the car – on their wedding anniversary, no less – to conclude unexpectedly lengthy signing talks with Kenny Dalglish.

But I would not have dared suggest Fallon had signed more world-class players than anyone in Celtic's history, save for the possible exception of Willie Maley. Now I have no hesitation in doing so. In fact, the names – Simpson, Gemmell, Auld, Murdoch, Dalglish, McGrain, Macari, Connelly, Hay and McStay – speak for themselves. Essentially, Fallon recruited most of one European Cup-winning team, then assembled another – arguably more talented – only to see them sold off before their potential could be realised.

Jock Stein recognised his eye for talent, trusted in it, and was richly rewarded. Fallon had free rein to recruit young players and was a constant companion on the manager's trips to assess signing targets and European opponents. Back at Celtic Park, he played an equally important role in soothing friction with the players, all of whom mention the Irishman's uncanny knack of knowing when to heal Stein-inflicted wounds. "Big Jock didn't do peacemaking," explains Billy McNeill. "Sean, with that Irish charm, was born for it. There would have been many more fall-outs without him around."

Even the relationship between Stein and Fallon has its surprises. It's no secret they worked well and closely together, but the extent of their friendship and ways in which their careers were intertwined is remarkable. I had no idea their families would enjoy day trips to the coast together, or that Stein – "Uncle Jock" – would accompany Fallon on the morning school run.

Fallon was the junior partner in their working relationship, but he was a man to whom Stein had been indebted since December 13, 1952. That was the date on which Fallon was made Celtic captain, recognising his position among the club's most established and influential players. Stein, by contrast, had joined just 12 months earlier and was still scrapping to earn a regular first-team place amid scepticism about his age and ability. Nonetheless, in selecting his deputy, the new captain opted not for established internationals such as Bobby Evans or Bertie Peacock, but for the journeyman centre-half just signed from non-league Llanelli. An injury to Fallon meant Stein took the armband just weeks later, and the rest forms the greatest chapter in the club's history. "A lot of people weren't happy with my choice," Fallon would recall. "But I saw something special in Jock."

Not for the last time, Fallon had been the first to identify extraordinary talent. Indeed, it was this same appreciation of Stein's unique abilities that enabled Fallon to selflessly and willingly stand aside in 1965 when his old pal was given the job he had been groomed for. "I could see that Jock was what Celtic needed," was his explanation.

The man with the inimitable, gravelly Sligo accent enjoyed a unique perspective on the most turbulent and successful period in the club's history, and shared with Neilly Mochan the distinction of having played his part in its two greatest triumphs. But while his contribution to Lisbon and the 7-1 win over Rangers was considerable, it would be a mistake to conclude Fallon's story begins and ends with black-and-white images and long-gone glories. He left Celtic with their best player of the 1980s and 90s in Paul McStay, and at Dumbarton maintained his knack for unearthing talent by signing the teenage Graeme Sharp and Owen Coyle. Sir Alex Ferguson, a long-standing friend, credits Fallon with having a major influence on the early stages of his managerial career.

If you're wondering why someone so extraordinary is consistently portrayed merely as "trustworthy" and "dependable", it is because his humility facilitated this typecasting. And perhaps that's what impressed me most about Fallon. Ask him about Dalglish and McGrain and he would say, "Ah, they were Celtic's signings, son. Not Sean Fallon's." Enquire about his playing achievements and he would stress how much better others were. Discuss the shabby way he was treated at the end and he would lament only that his departure broke Celtic's historic links with Sligo.

Fortunately, the men who worked with him had no such reservations. It had been my great hope that Sean would be recognised for the giant he is while still alive, through their words and this book – his book. But I realise now that's not important. Public recognition something he never craved. Sean Fallon died peacefully with his beloved family gathered round him, having enriched the lives of all those fortunate enough to have known him. Nothing I or anyone else could write can ever compete with that.