"Where— (a) an employee's contract of employment is renewed, or he is re-engaged under a new contract of employment in pursuance of an offer (whether in writing or not) made before the end of his employment under the previous contract, and (b) the renewal or re-engagement takes effect either immediately on, or after an interval of not more than four weeks after, the end of that employment, the employee shall not be regarded for the purposes of this Part as dismissed by his employer by reason of the ending of his employment under the previous contract."
"In our judgment, therefore, an employer 'proposes to dismiss' an employee if on an objective consideration of what the employer says or writes, the employer is proposing to withdraw the existing contract of employment from the employee, or the departures which the employer is proposing from the existing contract are so substantial as to amount to the withdrawal of the whole contract."