Kilner began the 1920 season with an innings of 206 not out in his first match, against Derbyshire, and the effort remained the highest score of his career. He batted for four hours, hitting 24 fours and two sixes. He could have been caught when he had scored around fifty, but a local newspaper described the innings as brilliant, his driving and pulling being particularly effective. Kilner appeared in one representative match: at the end-of-season Scarborough Festival, he played for CI Thornton's XI against the Marylebone Cricket Club (MCC) side which visited Australia in the winter—at the time, the MCC administered English cricket, and the England team toured under its name. In total, he scored 1,316 runs at an average of 37.09 with two more centuries, placing him second in the Yorkshire averages. With the ball, he took 27 wickets but his average of 25.33 was relatively high. The county finished fourth in the Championship as Middlesex were crowned winners. Critics believed Kilner should have bowled more frequently, an opinion shared by Wilfred Rhodes, Yorkshire's main slow left-arm spinner. Conscious of his increasing age, the 42-year-old Rhodes wanted support with the bowling workload; he considered Kilner the best option and encouraged him to improve his left-arm spin. Consequently, during the winter, Kilner practised bowling in the yard of the Wombwell hotel where his father was landlord. Around the same time he celebrated the birth of his second son, named Major after Major Booth.