The horn in a Hawker is really multi-purpose. Much like an attention getter.
From the training manual:
STALL WARNING AND IDENTIFICATION SYSTEM
General
A stall warning and identification system is provided to emphasize the aircraft's natural cues available at the point of stall. The system functions are:
Stick shaker (warning)
Stick pusher (identification)
The system comprises ywo sensing channels, each using an airflow angle sensor vane, a signal summing unit (SSU), and a third sensing channel which uses two underwing pressure-sensing vents and a stall identification sensor.
Warning and identification is provided by two stick shaker motors, and hydraulically operated actuator with two integral electrohydraulic valves respectively, and associated logic, announciators and test switches.
SYSTEM LOGIC
1. It is impossible for a stick push to occur before a stall warning (stick shake)
2. No single active fault of an SSU or relay can cause the operation of a stall valve or the associated red STALL VALVE annunciator.
3. The autopilt is disengaged when a stall warning signal is initiated. This prevents the autopilot from attempting to counteract the resulting stick shake operation or subsequent stick push.
STALL WARNING SYSTEM
The stall warning system uses an electrically driven stick shaker on each control column to provide a physical warning of an approaching stall to the pilots.
There is more but I'm knackered now!