“It’s Scotland, it’s League Cup final day here at Hampden Park where Celtic meet Partick Thistle, who have no chance.”

So began the BBC’s broadcast of the 1971 showpiece event. It wasn’t some controversial throwaway remark either: it was an apt barometer of the mood music of a nation. When Davie McParland led the Jags onto the famous turf at the national stadium to take on their neighbours across the city, the task facing them was essentially impossible. Or so it seemed.

Stein would guide Celtic to the league title and the Scottish Cup that season, as well as leading the Glasgow club to the semi-finals of the European Cup before they were eliminated on penalties by Inter Milan. It is no exaggeration to claim the Parkhead side as one of Europe’s finest that year, and here was little old Partick Thistle coming to spoil the party.

Nobody gave the Jags a snowball’s chance in hell, until something remarkable happened. Thistle caught the Celtic defence napping as club captain Alex Rae opened the scoring early on with a peach from the edge of the box. Then the Jags got another. Then another. Then another.

By the time the half-time whistle rang out, the Thistle players were pinching themselves in disbelief. Here they were, a team that had never won the League Cup, 4-0 up and coasting against one of Europe’s great sides.

Some were jubilant. Others kept their composure. But there was at least one among them – who admits he perhaps had other allegiances making their presence known in the back of his mind – who had one simple thought: not them.

“I don’t suppose we did really [understand the significance of the win,” Rae recalled Rae, speaking at the launch of Thistle's programme of celebrations to mark the 50th anniversary of their famous Scottish League Cup victory. “I grew up in Govan – and this isn’t giving anything away – and I grew up a Rangers supporter.

Glasgow Times:

“When we went in at half-time and we were 4-0 up, the very thought of not seeing the game through was horrendous. There were one or two of us that were getting a bit carried away but we soon put a stop to that. 

“It’s surreal. It’s as simple as that. You just try and concentrate on the ball!

“If you were a sensible person you would never have bet on us that day, you just wouldn’t. A couple of my pals put a bet on but surprisingly they only got odds of 4/1. But the bookies are rogues, aren’t they?”

When the news filtered across Glasgow that Thistle were 4-0 up and dishing out what remains Celtic’s heaviest ever defeat in a domestic cup final, there were those in Govan who decided to take in the action for themselves. Reports from that day tell of scores of Rangers supporters leaving Ibrox at half-time (whose own team were playing Motherwell and would go on to win 5-1) in order to race across to Hampden for the second half to witness their rivals' capitulation firsthand. Rae laughs: “That’s right! The taxi drivers must have made a fortune.”

Celtic would pull a goal back through Kenny Dalglish in the second half but the damage had already been done. That blistering first-half showing – unquestionably the Jags’ finest hour in a history spanning 145 years – had blown Stein’s superstars to smithereens.

Rae insists that he and his team-mates were always going to go for the jugular that afternoon, such was the mentality instilled in the squad by McParland. So much so that even after nudging Thistle ahead with that surprise early lead, the thought of setting up shop and holding what they had never crossed the players’ minds.

“No. Honestly, this is no bulls***,” Rae asserts. “If you look at the team then – it was a young team. I was 24 and I was one of the oldest players in the team. Hugh Strachan and Jackie Campbell were a couple of years older than me but the rest of them were all 18, 19, 20.

“Fair play to Davie McParland, he always encouraged us to go forward. At no stage do I ever remember him telling us to sit deep.

“Celtic clearly took us for granted. Six of our players went on to get caps which says something about the level of ability in the team. On our day we played good football.

“A lot of people say Celtic had the better chances in the second half but the first thing I remember was Dennis McQuade striking the ball from about 25 yards and it skimmed the crossbar. It was really a very competent performance – not necessarily all gung-ho and attacking, it was efficient defending too.”

As not only captain but the man who opened the scoring that day, Rae ensured his name will forever be etched into the history of Partick Thistle. He speaks fondly when he recalls his playing days at the club or the occasional visit to help with the half-time draw at Firhill, and admits that the Celtic players and supporters conducted themselves with dignity and humility in their defeat – even if the well-wishing didn’t last forever.

“I don’t recall any negative [from the players]. The Celtic fans were first class. But the following year I went with my wife to watch a Hibs-Celtic game and walking down the road I got a hell of a lot of abuse,” Rae recalls with a good-natured chuckle. “My darling doesn’t hear swear words!”

Jags fans can purchase from a range of 1971 commemorative packages at www.ptfc.co.uk/shop.