John Kenneth Edward Slack DL (23 December 1930 – 6 May 2012) was an English cricketer and judge. He was born at Marylebone, London. A right-handed batsman, Slack made his first-class debut for Cambridge University against Middlesex in 1954. He played 6 further first-class matches for the university in that year, the last coming against Oxford University. In his 7 first-class matches, he scored 434 runs at a batting average of 31.00, with two half centuries and a single century high score of 135. This came on debut against Middlesex. Outside of cricket he played rugby for Middlesex.