(1)     For the purposes of this section –

‘associated institution’, in relation to any single employer, means-

(a)     where the employer is a company, any other company which is associated with the employer company by reason of the fact that both companies are managed or controlled directly or indirectly by substantially the same persons;

(b)     where the employer is not a company, any company which is managed or controlled directly or indirectly by the employer or by any partnership of which the employer is a member; or

(c)     any fund established solely or mainly for providing benefits for employees or former employees of the employer or for employees or former employees of the employer and any company which is in terms of paragraph (a) or (b) an associated institution in relation to the employer, but excluding any fund established by a trade union or industrial council and any fund established for postgraduate research otherwise than out of moneys provided by the employer or by any associated institution in relation to the employer;