Working with his fellow Welshman Carwyn James, the coach of the side, John directed the most successful Lions side to tour New Zealand around the Test match grounds of the country as they claimed a 2-1 series win, the last game, at Eden Park, being drawn.
John came to New Zealand two years before the Lions trip on an ill-fated first visit by the Wales side that had dominated European rugby that season.
However, it was a nightmare trip as a rampant All Blacks team at what proved to be the zenith of a significant era beat them 19-0 and 33-12 in the two Test matches, fullback Fergie McCormick kicking a world record 24 points at Eden Park.
That performance made McCormick problem No.1 for the Lions two years later. James devised a plan to have his influence reduced during the series.
A week before the first Test, when the Lions played Canterbury in what became known as 'the Battle of Lancaster Park,' James kept John out of the game, had him sit in the stand and told him to concentrate on how McCormick played.
That resulted in John developing a tactical kicking plan with McCormick running all over Carisbrook in Dunedin, chasing well-placed kicks from John that did not allow him the freedom he had previously enjoyed when recovering the ball and instigating play.
The All Blacks lost 3-9, and McCormick never appeared for the All Blacks again.
The Lions were outplayed in the second Test as New Zealand won 22-12, courtesy of two tries by All Blacks first five-eighths Bob Burgess, a player many of the Lions established friendships with.
However, in the third Test, John was in his pomp, getting an early lead that left the struggling All Blacks no chance of responding and achieving a 13-3 win that ensured they could not lose the series.
That was wrapped up in the fourth Test, when JPR Williams, who died a month ago, landed a long-distance dropped goal to break a scoring deadlock for a 14-11 win.
Throughout his career, John feasted on his relationship with his halfback Gareth Edwards. The pair are still central figures in debates over the greatest of all time.
While John debuted against Australia in 1966, it was another year before he was paired with Edwards. It was claimed that when Edwards asked him where he would like to receive the ball, John said, 'You throw it, I'll catch it.'
Before departing for the Lions' tour, Wales achieved its first Grand Slam since 1952, beating France in Paris for the first time in 14 years. John shared three Five Nations titles, the Grand Slam, and two Triple Crowns with his Wales teammates.
During the tour of New Zealand, John revealed the ability to have a talented backline, which included players like Mike Gibson, John Dawes, David Duckham, Gerald Davies and JPR Williams, who played running rugby of a quality rarely seen.
Their 47-9 drubbing of Wellington led the capital city side to decide to change their game style, and the free-running style has been a trademark of the province since then.
John established a scoring record on the tour that will never be broken when among the 180 points he posted were 30 of the 48 points the Lions scored in the Test series.
Changes from the long tours of the amateur era mean John's scoring feats will have no chance of being bettered.
Yet, despite his dominance, his career was over 12 months later. The pressures of his new-found superstardom became too great, and he bowed out of the game at 27 years old.