20
(b)
one or other of those conditions would be fulfilled if the business of the employing company and the business of the associated company (or, if more than one, each of the associated companies) were treated as together constituting one business,
that condition shall for the purposes of this Part be taken to be fulfilled in relation to
the dismissal of the employee.
(4) Where an employee of a company is taken into the employment of another company which, at the time when he is taken into its employment, is an associated company of the first-mentioned company, his period of employment at that time shall count as a period of employment with the associated company, and the change of employer shall not break the continuity of the period of
employment.
(5) For the purposes of this section two companies shall be taken to be associated companies if one is a subsidiary of the other, or both are subsidiaries of a third company,
and "associated company" shall be construed
accordingly.