removing tow ball

[oldnick]

herewith an entry in the stupidest question of the year category

want to remove the ball .....factory fitted FL my2000
turn the plastic knob [ which locks the ball casting in place presumably ] , insert the tiny key , try clockwise and anticlockwise , try to pull down
nothing ...perhaps a tiny sideways movement
tried a second pair of hands ...still nothing

am I missing something ? a lump hammer on the ball didn't help !