IT has been a cause of some perplexity to many Celtic supporters that their club has only achieved the feat of winning the Treble three times in their history.

Other than Martin O’Neill’s clean sweep in his maiden season in 2000/01, you have to go back the Jock Stein golden era and seasons 1966/67 and 1968/69 which is surprising given subsequent dominant periods.

One man alone cannot be held responsible, but if the Celtic supporters are searching for a villain then Joe Harper fits the bill as the Pittodrie striker was a key protagonist in preventing the grand slam on two occasions.

Celtic had already wrapped up the League Cup and the League title and were on their way to their second European Cup Final when Harper scored the opening goal in the 1970 Scottish Cup Final as the Dons went on to stun Jock Stein’s side with a 3-1 victory.

He also set up both goals in the 2-1 extra time win in the League Cup Final of 1976/77 – a season when Celtic went on to reclaim the title and lift the Scottish Cup.

On both occasions, the Dons were massive underdogs – just as they are tomorrow. However, the 68-year-old, who is Aberdeen’s record scorer with 205 goals, believes they can upset the odds just like the Reds did in the seventies.

Harper said: “This is the chance for these Aberdeen players to become legends at the club. What more do you need to inspire you?”

“It depends how everyone reacts on Sunday because we’ve got guys that haven’t been to a cup final but I’m hoping they will be buzzed up and play even better than normal.

“We’ve got good players and the good thing is they are going into this game on great form as they played Inverness Caley off the park last week.

“I don’t have any fears about it. If the players have the right ambition then Celtic are beatable.”

Harper was only 22 and playing in a cup final for the first time when the Dons won an early penalty against Celtic in 1970 and he was given the responsibility – but had to wait nearly nine minutes to take it as the Celtic players argued with referee Bobby Davidson

He recalled: “It was massive moment. However, the funny thing was I wasn’t nervous at all. I was very confident in my own ability to take penalties and I wasn’t going to change my style because it was the cup final.

“I always used to run up as if I was going to hit it to the goalkeeper’s left hand corner and then at the last minute turn my foot and hit the ball into his right hand corner.

“It was probably the best penalty I have ever taken because it actually went into the side-netting. It was a dream, really.”

Derek McKay – who became known as Cup-tie McKay as he also scored the winning goals in the quarters and semis – scored twice either side of a Bobby Lennox goal in the last 10 minutes to spark wild Aberdeen celebrations.

Harper said: “What a lot of people forget that is we played Celtic at Parkhead two weeks earlier and beat them 2-1.

“Eddie Turnbull thought they would kick me so he put me in the reserves at Tynecastle and I scored a hat-trick.

“So it wasn’t a surprise to us that we would go out and beat Celtic in the final.

“Cup-tie McKay had the game of his life.

“For the first goal he flicked the ball over Tommy Gemmell’s head and played it into me. I played it through to Jim Forrest and his shot was deflected to the back post and Derek stuck it in the net.

“If you got a goal like that today from Barcelona or Real Madrid you be talking about it for years.

“Celtic, of course, put a bit of panic in the team when they scored with about four minutes to go.

“But then Martin Buchan hit a long ball up the right wing and I got it. I actually stumbled as I thought about going past Tommy Gemmell on the right side and having a shot at goal.

“So I ended up coming in to the left and when I realised I couldn’t get a shot away I knocked the ball to Derek and he thumped it into the back of the net.

“There is no greater feeling that winning a cup final and I’m a great believer that you want to do it against the best teams.”

Having moved to Everton and then Hibs, Harper came back to Pittodrie in 1976 under the inimitable Ally MacLeod and was instrumental in the League Cup success which was literally a dream for goalkeeper Bobby Clark.

Harper said: “We went to Gleneagles before the game and stayed overnight and I was chatting with Bobby with a few boys around us at breakfast when he said ‘I had funny dream last night. I dreamt big Davie Robb came on as a substitute and scored the winner’.

“So of course, you can imagine how we all felt when that’s exactly how it all worked out.”

“We lost the opening goal to a controversial penalty when Drew Jarvie was penalised for tackling Kenny Dalglish.

“But we got an equaliser when Arthur Graham hit a ball to the far post, I put it back across goal and Drew came in to head it into the net.

“Then in extra time, Arthur’s shot deflected into my path and I managed to get a toe to the ball to divert it enough to Davie Robb who drove it into the net from close range.

“It was great because Davie was one of those unsung heroes. He was a real minder for the boys on the park. If there was any trouble, he would sort it out.

“He never got the praise that others got so it was great that he scored the goal that won the cup.”