2. If, before he has discharged his liability under the undertaking, a regular policeman—
(a)retires without an award other than one of the amount of his aggregate pension contributions in respect of the relevant period of service;
(b)leaves his police force on joining the Royal Ulster Constabulary with the consent of the police authority;
(c)dies, or
(d)is dismissed,
all further liability under that undertaking shall cease.