Didn't the Premier Leage originally have 22 (24?) teams? In the early to mid 90's some restructuring was done to reduce it to the current 20. This involved relegating four teams and only promoting two from Division One. Not sure what year it was though. 93? 94?
Hmm... the Premiership started in 1992/93 season I think. I think it's when it went from 20 teams (old 1st Division) to 18 in the Premiership (4 relegated and only 2 promoted). Then it changed again from 18 to 20 several years ago.