Complex sentence: The story centres on Gabbert building his exclusive during the latter stages of the 1962/63 season, a time when Kay is becoming known as one of the best players in the game, having joined Everton, with whom he wins the League title.
Split into simpler sentences: The story centres on Gabbert building his exclusive during the latter stages of the 1962/63 season. A time when Kay is rising to be considered one of the best players in the game, having joined Everton with whom he wins the League title.