I have an employee who has given notice that she intends to leave to go to another job. She has no start date for that job, so has stated that she will leave in 4 – 7 weeks time. All our contracts clearly state that the employee must give 4 weeks notice. need to replace her and I need to give her replacement a firm start date. Am I obliged to honour her request or can I insisit that she leaves on the 28th day after the date of her letter?