John was simply sensational in the Land of the Long White Cloud as the Lions finished 2-1 winners thanks to a 9-3 victory in the first Test, a 13-3 success in the second and a 14-14 draw in the final international.
A total of four more Lions squads have visited New Zealand since John's men swept all before them 40 years ago but none has matched their achievement.
The last pride to travel Down Under were beaten 3-0 in 2005 and John would be surprised to see future tourists down the All Blacks in their own backyard.
"Our feats have never been achieved in New Zealand since. The odd Test match has been won, but winning over the course of a three-Test campaign down there is as close to an impossible task as you will get in rugby," John wrote in his column in the Western Mail.
"If anything, I believe it will get harder for the Lions, given the close proximity of games on tours these days and how you can't put that intensity needed to beat New Zealand together three weeks on the trot.
"Equally, my record out there of 180 points on that tour will never be beaten, if only because there aren't enough matches for anyone else to do it in.
"It's a record I remain immensely proud of, although winning as a team was far more important."
And while John himself admits the 2017 Lions must climb a massive mountain if they are to win in New Zealand, he says the fact that he and his team-mates were written off so heavily four decades ago made their on achievement even more special.
Very few critics took the Lions seriously in '71 and next to no one tipped them to return home with a series win. And when the tour began with defeat to Queensland during the first of two fixtures in Australia, the Kiwi public refused to believe that the Lions could come close to troubling their beloved All Blacks.
"We had been foolishly written off by New Zealand players, pundits and media as the tour began," added John.
"Another poor advert for British rugby, they said, a team who were going to prove easy meat for Colin Meads' men in black.
"Well, as predictions go, it was right up there with Michael Fish 'there won't be a hurricane'!
"Even though we kept on winning our warm-up games, people Down Under were still sceptical... until we really put down our marker by thrashing New Zealand champions Wellington 47-9 a week ahead of the first Test. We shook New Zealand rugby to its core by winning the opening Test in Dunedin by a 9-3 margin…the rest is well known."