Why the Gannet replacement needed pulse-Doppler radar

Why did the Royal Navy want pulse-Doppler radar for the Gannet airborne-early-warning replacement?

It offered very long-range detection of moving aircraft, trading some altitude precision for the earlier warning essential to fleet defense.

An airborne early-warning aircraft must find moving targets at long range against sea and land returns. Pulse-Doppler processing uses relative motion to separate aircraft from much of that background. Early systems might provide less precise altitude information than operators would like. The Royal Navy could still value the technology because detecting the raid earlier gives fighters and ships more time to react.