I am quite sure you would still be liable... if you dont leave enough of a gap for you to stop, then its your fault. I think insurance companies would look into greater detail if somthing went drastically wrong anyway, so it probably wouldnt matter in any case. 
Indeed you would...something lost in translation with my previous posts...
I was merely taking the micky out of out Winter Tyre legislation expert Ben, wo tried to say if you hit someone with winter tyres on the front only you'd be liable, but if they were on the back only you wouldn't.
It's palinly stupid...if you hit ANYONE it's your failt.