Helm: probably not a meter, but it went from being pretty moppish to nearly touching my ass in that time. I have really high metabolism, eat like a fat bastard, and in general everyone on my mother's side has really thick hair that grows in extremely fast (my grandfather wore hair about a foot shorter than yours his whole life :p) I usually just go between getting it cut short and growing out a mop every 2 months.
Plus, and I can't confirm this since I haven't done any reading on it, but a friend of mine (whose hair also grows really, really fast, faster than mine; he goes from a shaved head to his trademark mohawk in about a month) that smoking a lot of pot (which is bad kids) contributes to hair growth, which would explain some of it in both of our cases.
Finally, two things to keep in mind.
1) Even though my metal genes aren't physically expressed, my grunge chromosomes are raging.
2) If I was going to lie about the growth of anything on my body, it wouldn't be my hair.