Can't, or I won't compress spring enough to fit to my Rover

[rumpelstiltskin]

I've replaced a few springs on my cars over the years and have a rough idea as to how much you have to compress a spring before fitting it to a strut.Im replacing a front spring on my rover 75 diesel.Old broken springs off, and with the aid of my newly acquired new spring compressors I have the spring under so much tension im fearing for my compressors, and ofcourse my life!
I feel like I've gone way beyond normal compression and im still about an inch and a half off getting the top nut on the strut shaft??? The centre shaft is fully uncompressed at its full length, I dont know whats going on?
I've actually had a Halfords set of spring compressors in the past skip a few threads under tension!! Never rmoved so fast in my life! I thought to start with it was just a confidence thing due to this previous experience but I've ruled that out, spring is easily compressed enough.