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

A contract of employment may come to an end when an unforeseen event makes performance of the contract impossible or radically different from what the parties originally intended. The contract is then said to have been “frustrated”.

When a contract is frustrated it ends automatically by operation of law, without a dismissal on the part of the employer or a resignation on the part of the employee, and the parties are discharged from further obligations under it.

Frustration of employment contracts is most likely to arise in cases where an employee suffers a prolonged or sudden illness or disability, or is imprisoned. But it can also happen where there has been a change in the law which makes