From what I remember, the Red Top was the first to incorporate a cooled seeker which gave it the capability against supersonic targets, guiding on the heat generated by skin friction. I once chased a stern shot Red Top fired by the Sqn boss at STCAAME before it became AGWOEU (Welsh for STCAAME). The first missile came off (was only meant to be one) and departed stage right. The second came off and went dead straight to the target. Shortly afterwards, the first missile took the target out as well! The analysis was that Red Top is a lazy missile!