Rapier is a very important element in our armoury of defence against attack from the air. At low to medium altitudes the attack comes from all-weather, contour-following, very fast and very expensive aircraft, through much more numerous and diverse conventional aircraft limited to fair-weather operation, to helicopters and reconnaissance drones.

The perfection of radar makes the high open sky a dangerous place to be. Aircraft are best used, like any other weapon, when they enjoy the greatest advantage. They will therefore, fly high enough to see their objective (stationary or slow-moving targets) but low enough to gain concealment from radar surveillance.