4. Where a person wishes to make a surrender he may—
(a)in the case of a pensionable employee who on ceasing to hold his employment becomes entitled to a retirement pension (in this schedule referred to as “a retiring employee”) not more than 2 months before or within one month after the date on which he ceases to be employed; and
(b)in the case of a pensionable employee who would, if he were to retire from his employment, become entitled to a retirement pension (in this schedule referred to as “a continuing employee”), within 2 months before or at any time after becoming a continuing employee and while he is still employed,
notify his desire to surrender a part of that retirement pension by completing a copy of the form specified at the end of this schedule, or a form to the like effect, and sending it to the appropriate administering authority;
Provided that where the appropriate administering authority are satisfied that it has not been reasonably practicable for a retiring employee to notify his desire to surrender a part of a retirement pension within the time limit imposed by sub-paragraph (a), owing to circumstances beyond his control, they may at their discretion extend that limit to a date not more than 6 months after the date on which he ceases to be employed.