At what point can an employer justify “frustration of contract”?

The general principal is that frustration only applies where there has been some extraneous change of situation not foreseen or provided for by the parties at the time of contracting, which makes it impossible for the contract to be performed or at least renders its performance significantly different from what the parties contemplated when they entered into the contract.

Frustration most commonly occurs in the context of long-term absence due to illness or incapacitation, or where an employee leaves the jurisdiction without notice to the employer.

The Courts may have regard to a number of factors in determining whether or not the contract, and indeed at what point the contract has become