The employment relationship is terminated by the employer, it is a case of dismissal. If the employee terminates the employment relationship, it constitutes a resignation. But there is, in principle, nothing preventing an employer and an employee from concluding a contract to terminate the employment contract a mutually agreed termination of employment. If it is really the case that there was a mutually agreed parting of the ways, there could be no claim of unfair dismissal, simply because there was no dismissal in the first place.
For further information on Unfair Dismissal or any labour related matters, you can contact Bernard Reisner: