My vote here goes to John De Mendoza. He had been a high ranking player in the early-mid 60's but then retired. He returned to his club in the late 70's and practiced daily against the wall for several hours from 7 am. John entered the club tournament and I had the privilege of playing him in the first round. After a predictably short match, I congratulated him and enquired about the fact that he had played with a wooden racquet with no grip. He informed me that it was 'the only pure way to play tennis'!