(1) A participating issuer shall not change a unit of a participating security from uncertificated to certificated form except -

(a) where permitted by the rules made and practices instituted by an operator, or

(b) following receipt of an operator-instruction requiring the conversion into certificated form of uncertificated units of a participating security registered in the name of a system-member, or

(c) subject to regulation 16, following receipt of an operator-instruction requiring the registration of a transfer of title to uncertificated units of a security to a person who is not a system-member, or

(d) on the registration, in accordance with regulation 36 (2), of an offeror who is not a system-member as holder of the units of the security referred to in that regulation.

(2) In the circumstances specified in paragraph (1) (b), (c) and (d) a participating issuer shall -