The Vickers 40 mm QF 2 pounder "Pom-Pom" gun anti-aircraft mounting was introduced to the Royal Navy in the early 1930s.
It was, therefore, essential to aim the mount from a remote location, using a director that had a clear view, free from smoke and vibration.
The gun crew would then move the mount to match the pointers rather than having to try and aim at the target aircraft.
[1] These directors began to appear on Royal Navy cruisers, battleships and aircraft carriers in 1930.
[3] The Mk IV director was a considerable improvement and used gyroscopes in a gyro rate unit coupled to an optical rangefinder and Type 282 radar to determine the range, speed and direction of enemy aircraft and then used an on-director computer to produce an accurate fire control solution to hit the target.