It was made illegal in 1991. I was born in 1988 so it was still legal in my lifetime.
I actually only found this out recently as I'm doing an access to law course at college and I'm still completely 
that it was legal for so long and within my lifetime.
I actually have an essay to write and I have to talk about the case which resulted in it becoming a criminal offence and it got me thinking about it again.
Seriously though, wtf! Why was it made illegal earlier? I think if someone had asked me prior to starting my college course when it was made a illegal I probably would have assumed the 1960's or the 70's at a push but the 1990's! Seriously!