"There have only been four successful Lions tours in history and amazingly Ian McGeechan has been involved in three of them, as a player in 1974 and as a coach in 1989 and 1997," Campbell told IrishRugby.ie.
"That is why I've such confidence in McGeechan having the Lions primed for their best performance of the tour this weekend. If anyone knows South Africa and how they tick, Ian McGeechan does.
"I don't necessarily think it is a must win game for the South Africans. They could still lose this and win the series, but I think for the Lions to win the series they simply must win the Test on Saturday."
Campbell himself toured twice with the Lions in 1980 (South Africa) and 1983 (New Zealand) and 29 years ago last week he made his Test debut in the famous red shirt.
"South Africa 29 years ago was a mixture of anticipation, excitement and nerves. I came on as a substitute for my first Lions Test.
"It was the second Test. We were losing 16-15 with about fifteen minutes to go. I came on and Ray Gravell's welcome to me when I came on wasn't good luck or anything tactical.
"He was concerned with how he was playing. He said, 'how am I playing?', I said: 'You are playing very well Ray', and he said: 'Well, do you think I will get selected for the third Test?'
"That was my welcome onto the field in Bloemfontein for my first Lions Test. I think things have moved on slightly since those days," says Campbell who believes the current Springboks' build-up to the series may impede their chances.
"A factor that could come into it is the natural confidence and even the arrogance of the Springboks. They feel that all they have to do is turn up and they will win the series.
"It's a big risk for them to have pulled all their players out of the provincial games.
"A quote from their coach Peter de Villiers last week was remarkable when he said he was conscious that they hadn't really played a proper match for five or six months and that they would be using the first 20 minutes of the first Test as match practice.
"That is an extraordinary thing for any coach of any side to say at any time, never mind before a match of such significance as this."
In 1997, then assistant coach Jim Telfer told the Lions that the Test games they were about to play were their Everest and Campbell agrees.
"Test matches on every single Lions tour in history have a different dimension than any of the other matches that you play in. They take on a life of their own, a step-up for some into the unknown.
"They are at an all-together different level than anything the players would have experienced in the last six games, but they are all experienced international players, no matter what team McGeechan announced," says Campbell who scored 60 points during the 1980 tour.
That tour brought the battle between Campbell and fellow Irishman Tony Ward for the first choice out-half position that had raged on the national stage all the way to South Africa with the Lions.
Campbell and Gareth Davies were the original out-half selections before Campbell pulled a hamstring in the first week and a shoulder injury to Davies brought Ward in as a replacement.
"You can imagine how happy I was to see Tony arriving in South Africa, having, I thought, seen the back of him with Ireland in Australia in 1979!"
Ward played in the first Test after only arriving that week, kicking 18 points, but the Lions lost in injury-time, 26-22.
Davies returned for the second Test only to have his tour ended by a knee injury in Bloemfontein and Campbell came off the bench to become the Lions third out-half in two games, then starting the third Test.
The atrocious conditions of the third Test are well documented, unlike the story that could have ended the Campbell-Ward rivalry.
"I played the third Test in Port Elizabeth in absolutely horrendous conditions," begins Campbell.
"Tony Ward was on the bench that day and he forgot his boots.
"The only person with a spare pair of boots was Colin Patterson who had a pair of moulded soles training boots. They were only size 7 and Tony wore size 8 ½," the former Lion out-half says with a slight laugh.
"Just before the team ran out into these horrible conditions in Port Elizabeth, the replacements left for their seats way up in the stand.
"By the time Tony goes up and sits in his seat we have run out and kicked off. The ball goes loose within thirty seconds.
"I've gone down on the loose ball and the South African openside takes a swipe at the ball as I go down on it and he caught me on the eye. I have the scar to show to this day," he says, pointing above his eye.
"I was pumping blood. This was in the years before blood substitutions. I bravely played on, little knowing that Tony was up in the stands praying like he never prayed before or since, that he would not have to come on with his size 7 moulded boots.
"As I always say to him ever since, if I had known the situation he was in, I would have come off and finished his career there and then," he remarks jokingly.
Campbell kicked nine drop goals in his two Lions tours, which is still a record, and helped them record a win in the final Test match in South Africa, something no other Lions team has managed.
"Nobody cares. At the end of the day, every Lions tour is rightly judged by how it does in the Test matches and we lost 3-1," Campbell explained, before bringing the conversation back to this weekend's game.
"It is a question about getting the minds right - cool, calm and collected - and being ready for the performance of their lives.
"They will take great confidence from the fact that they have played six and won six. There is a lot at stake and they will be keen to hit the ground running, play the way they've tried to play up to now.
"The Lions are battle-hardened on the one side and the Springboks on the other side are a little undercooked although maybe a little bit fresh too.
"I would be quietly confident. I think the South Africans are still the favourites for the series but one step at a time and the Lions have a very good chance of winning the first Test."
The key to Saturday's game, according to Campbell, will be the breakdown and place-kicking.
Heinrich Brussow starts in place of the injured Schalk Burger in the hosts' back row and his effectiveness up front and that of out-half Ruan Pienaar and full-back Frans Steyn, on whom the kicking duties rest, will go a long way to deciding the result of the first Test.
"The South Africans, so far on the tour, seem to have had the upper hand in the breakdown.
"That is really a massive area for the Lions to sort out before the Test match and as in all tight Test matches, place-kicking could be absolutely crucial and the Lions have the edge in that department."
Twelve years of waiting is now over. The Lions want another scalp of the World champions, while South Africa will seek revenge for what played out in 1997.
Campbell added: "We are on the verge of the real thing. It will depend on the success or failure of the actual Test matches and not the tour matches.
"If the Lions can win, the tour is going to take off. If the Lions lose, it is going to be a very long last two weeks in South Africa."