I'm sorry to say I know next to nothing about the British R.K.T. Records, other than that they were situated in Syston, Leicester according to the contact address (I think it translates "Hicksville" in International English..) and the fact that they released the first albums featuring cover art by reknowned graphic artist Dan Seagrave. Stylewise their roster mostly played in the Thrash- and crossover field, though I'm sorry to say, none of these acts could be considered "major players". An exception is the rare but excellent MASQUE mini - one of England's finest post-NWOBHM recordings.

I'm not 100% sure they didn't released anything before or inbetween MASQUE and the compilation, but if I had to make a bet I'd say this was their complete discography.