You can’t fire someone at will any more
Every employee has the right not to be unfairly dismissed. He is protected against arbitrary dismissal, being dismissal without substantive grounds and/or in a procedurally unfair manner.
There are three – and only three – legitimate categories of “Substantive Grounds”,
(b) Incapacity (itself divided into ‘inadequate performance’, ‘ill-health and injury’ and ‘incompatibility’) and
(c) ‘operational reasons’ (retrenchment).