Picture this: Glasgow, a city gripped by European football fever. On the evening of 19 April 1972, something remarkable happened. Both of the city's footballing giants were hosting European semi-finals simultaneously—a logistical spectacle unimaginable in today's game. While Rangers faced Bayern Munich at Ibrox in the Cup Winners' Cup, a colossal crowd of 75,000 packed into Celtic Park for a true clash of footballing philosophies.

Celtic, the swashbuckling, attacking force under Jock Stein, welcomed the legendary defensive masters of Inter Milan for the second leg of their European Cup semi-final. The atmosphere was electric, a testament to an era when stadiums were cauldrons of raw passion. Adding to the unique drama, the Rangers match was chosen for live Scottish television, meaning Celtic fans had to wait for their own epic to be broadcast live only after the Ibrox game concluded.

Stein, a master tactician, had predicted Inter's approach. He knew the Italians, missing their star striker Roberto Boninsegna, would arrive with a singular mission: to defend, disrupt, and slow Celtic's flowing game to a crawl. His prophecy was spot-on. Yet, in the opening exchanges, Celtic's famous attacking verve shone through. As one contemporary report vividly described, Celtic "swarmed like excited ants" in the Inter penalty area during a furious and dominant first 15 minutes, creating a flurry of early chances that promised a night of high drama.