i've had a bet with my boss & i'm sure this rule was introduced in the 1950s when teams were wasting time by kicking it out (on the full) & at that stage it was a boundary throw in, he reckons it was in the 1970's or at the earliest the late 1960's
the bet is i have 1945-1965
he has 1966-too now
any articles would be good to print off, presuming i'm correct

thanks spelly or whoever else knows